Editing M1 Abrams (section)

==Design==

===Countermeasures===

====Camouflage====
[[File:M1A1 Twin Bridges training area 2C Republic of Korea 1-23 Infantry.jpg|thumb|left|U.S. M1A1s during the [[Foal Eagle]] 1998 training exercises in South Korea, with their factory single green paint scheme]]
{{further|Military camouflage}}

Some XM1 FSED pilot vehicles and XM1 LRIP tanks were painted with the [[MERDC camouflage|Mobility Equipment Research and Design Command]] (MERDC) 4-color paint scheme.{{sfn|Zaloga|2019|p=6}} Factory-applied [[forest green]] paint gave way to "Europe 1", a three-color pattern, in 1983 at the same time as [[Chemical Agent Resistant Coating]] (CARC) was adopted. Europe 1 consisted of Green 383, Brown 383, and black colors.{{sfn|Zaloga|2019|p=7}}

U.S. Army Abrams deployed to the Iraq War were painted Carc Tan 686A.{{sfn|Zaloga|2019|p=22}} Due to the increasing significance of American operations in Europe, the U.S. Army transitioned most of its vehicles to CARC Green 383 starting around 2017.{{sfn|Zaloga|2019|p=32}}

M1A1s came from the factory with the NATO three color camouflage Black/Med-Green/Dark-Brown CARC paint jobs.{{Citation needed|date=April 2008}} Today, M1A1s are given the NATO three color paint job during rebuilds. M1s and M1A1s deployed to Operation Desert Storm were hastily painted [[desert tan]]. Some, but not all, of these tanks were repainted to their "authorized" paint scheme. M1A2s built for Middle Eastern countries were painted in desert tan. Replacement parts (roadwheels, armor skirt panels, drive sprockets, etc.) are painted olive green, which can sometimes lead to vehicles with a patchwork of green and desert tan parts.

[[File:Armoured vehicles parading through Darwin on 25 April 2015.jpg|thumb|right|M1A1 in the Australian Army's Disruptive Pattern Camouflage, used for vehicles and [[materiel]].]]
Australian M1A1s are camouflaged in AUSCAM, a scheme that consists of black, olive drab, and brown.{{sfn|Zaloga|2019|p=40}}

====Concealment====
The turret is fitted with two six-barreled [[M250 grenade launcher|M250]] [[smoke grenade]] launchers (USMC M1A1s used an eight-barreled version), with one on each side. When deployed, the grenades [[Air burst|airburst]], creating a thick smoke that blocks both visual and [[Thermography|thermal imaging]]. The engine is also equipped with a vehicle engine exhaust smoke system (VEESS) that is triggered by the driver. When activated, fuel is sprayed into the hot turbine exhaust, creating thick smoke. This system was discontinued by the U.S. Army after it switched to JP-8 jet fuel in the 1990s{{sfn|Green|Stewart|2005|p=62-65}} due to the risk of fire.{{citation needed|date=January 2024}}<!-- Are the Intellitec Multisalvo M6 smoke grenade launchers worth mentioning?{{Sfn|Green|Stewart|2005|p=105}}-->

====Armor====
{{further|Chobham armor}}
{{multiple image
| perrow            = 2
| total_width       = 300
| image1            = M1 Abrams Hull Front Special Armor.jpg
| image2            = M1 Abrams Turret Bustle Side Special Armor.png
| image3            = M1 Abrams Hull Side Special Armor.jpg
| image4            = M1 Abrams Gun Shield Special Armor.jpg
| footer            = Configuration of M1 Abrams Chobham Special Armor. Clockwise from the top left: hull front, turret bustle side, gun shield, hull side.
}}
[[File:M1A Abrams im Taunus.jpg|thumb|Tankers drive an M1A1 Abrams through the [[Taunus|Taunus Mountains]] north of [[Frankfurt]], [[Germany]] during Exercise Ready Crucible in February 2005.]]
[[File:Trident Juncture 18 - U.S. Marines advance on Folldal 4871351.jpg|thumb|U.S. Marines with the 2nd Tank Battalion, [[2nd Marine Division (United States)|2nd Marine Division]], advance on their eastern objective defended by opposing [[Spanish Army|Spanish forces]] during [[Exercise Trident Juncture 2018|Exercise Trident Juncture]] 18 near Dalholen, [[Norway]], 3 November 2018.]]

In addition to conventional [[rolled homogeneous armor]] (RHA), the Abrams uses a secret British-developed Chobham [[composite armor]].

The M1 Abrams composite armor (referred to as "special armor" by the U.S. Army){{sfn|Green|Stewart|2005|p=18}} is most substantial at the front of the hull, where it is {{convert|2|feet}} at its thickest.{{sfn|Green|Stewart|2005|p=102}} The front of the hull is armored with composites. The Abrams turret features composite armor across both the front and the sides.<ref name="Special Armor classification">{{cite report |author1=PEO Close Combat Vehicles |title=Special Armor Security Classification Guide |date=16 February 1988 |url=https://static.warthunder.ru/upload/files/CIA-RDP91B00390R000300220014-8_18526c536b61b903b78d1571c3476c70.pdf |access-date=1 January 2024 |archive-date=28 December 2023 |archive-url=https://web.archive.org/web/20231228070557/https://static.warthunder.ru/upload/files/CIA-RDP91B00390R000300220014-8_18526c536b61b903b78d1571c3476c70.pdf |url-status=dead }}</ref>

The armor is much thicker on the Abrams than on previous tanks. This is not a reflection of any weakness of Chobham armor—pound-for-pound Chobham is better at stopping shaped charges and kinetic projectiles. Rather, unlike RHA, Chobham is optimized against shaped charge projectiles. Effective shaped charges, particularly [[anti-tank guided missiles]], were a relatively new battlefield innovation. Lacking a breakthrough advance in novel armor material to negate shaped charges, previous tank designers had simply not found it practical to add the amount of RHA required to defeat shaped charges.{{sfn|Kelly|1989|pp=111–140}}

While the exact composition of the Abrams' composite armor remains a state secret, a generalization about how it works can be gleaned from what has been publicly said about it. It consists of ceramic blocks set in resin between layers of conventional armor.{{sfn|Green|Stewart|2005|p=96-97}}{{refn|group=nb|name=Chobham|Chobham could also incorporate nylon micromesh and/or [[titanium]]<ref>{{cite news |last1=Hambling |first1=David |title=Breakthrough ballistics |url=https://www.theguardian.com/science/2001/oct/11/physicalsciences.technology |access-date=1 January 2024 |work=The Guardian |date=11 October 2001}}</ref>}}{{sfn|Zaloga|2019|p=6}} The ceramic acts as a [[non-explosive reactive armor]] (NERA), disrupting [[shaped charge]]s. The NERA plates shatter on impact with the projectile, disrupting the penetrating jets of shaped charges; or in the case of kinetic rounds eroding the projectile.{{sfn|Green|Stewart|2005|p=96-97}}

For the M1 Abrams base model, military historian [[Steven Zaloga]] estimates the frontal armor at 350&nbsp;mm vs APFSDS and 700&nbsp;mm vs HEAT warhead in the book, ''M1 Abrams Main Battle Tank 1982–1992'' (1993).<ref>{{harvnb|Zaloga|Sarson|1993|pp=9–10}}: Zaloga gives another set of figures in this book {{convert|350|mm|abbr=on}} against APFSDS and {{convert|700|mm|abbr=on}} vs HEAT.</ref> In ''M1 Abrams vs T-72 Ural'' (2009), he uses Soviet estimates of {{convert|470|mm|abbr=on}} vs APFSDS and {{convert|650|mm|abbr=on}} vs HEAT for the base model Abrams. He also gives the Soviet estimates for the M1A1, {{convert|600|mm|abbr=on}} vs APFSDS, and {{convert|700|mm|abbr=on}} vs HEAT.<ref name="T-72vsM1">{{harvnb|Zaloga|2009|p=15}}: Author mentions that a Soviet report estimated the protection of the basic M1 to be equivalent to {{convert|470|mm|abbr=on}} steel armor against armor-piercing rounds and equivalent to {{convert|650|mm|abbr=on}} steel armor against shaped charge warheads.</ref>

Armor protection against [[Kinetic energy penetrator|kinetic energy rounds]] was improved by implementing a new special armor incorporating [[depleted uranium]] (DU). This was introduced into the M1A1 production starting October 1988.{{sfn|Hunnicutt|2015|p=245}} but at the expense of adding considerable weight to the tank, as depleted uranium is 1.7&nbsp;times denser than [[lead]].<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/in_depth/2860759.stm |title=BBC: US to use depleted uranium |work=BBC News |date=18 March 2003 |access-date=9 June 2009 |url-status=live |archive-url=https://web.archive.org/web/20090519090657/http://news.bbc.co.uk/2/hi/in_depth/2860759.stm |archive-date=19 May 2009}}</ref> The DU is applied to the backing plate of the turret armor arrays.

The first M1A1 tanks to receive this upgrade were tanks stationed in Germany. US-based tank battalions participating in Operation Desert Storm received an emergency program to upgrade their tanks with depleted uranium armor immediately before the onset of the campaign. M1A2 tanks uniformly incorporate depleted uranium armor, and all M1A1 tanks in active service have been upgraded to this standard as well.<ref name="Clancy">{{cite book |last1=Clancy |first1=Tom |title=Armoured Warfare: A Guided Tour of an Armoured Cavalry Regiment |date=1996 |publisher=HarperCollins |location=London |isbn=978-0-00-255525-8 |page=58 |url=https://archive.org/details/armouredwarfareg0000clan |access-date=1 January 2024}}</ref> This variant was designated as the M1A1HA (HA for Heavy Armor).<ref name="Zaloga_Sarson_11">{{harvnb|Zaloga|Sarson|1993|p=11}}</ref>

The M1A1 AIM, M1A2 SEP and all subsequent Abrams models feature depleted uranium.<ref>{{Cite journal|date=August 2006|title=The Army's Future Combat Systems Program and Alternatives |url=https://www.cbo.gov/sites/default/files/cbofiles/ftpdocs/74xx/doc7461/08-02-army.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.cbo.gov/sites/default/files/cbofiles/ftpdocs/74xx/doc7461/08-02-army.pdf |archive-date=2022-10-09 |url-status=live|journal=Congressional Budget Office Study|page=67}}</ref> Each Abrams variant after the M1A1 have been equipped with depleted uranium armor of different generations. The M1A1HA uses first-generation armor, while the M1A2 and M1A1HC use second generation depleted uranium. The M1A2 SEP variants have been equipped with third-generation depleted uranium armor combined with a graphite coating.

For the M1A1HA, Zaloga gives a frontal armor estimate of {{convert|600|mm|abbr=on}} vs APFSDS and {{convert|1300|mm|abbr=on}} vs HEAT in ''M1 Abrams Main Battle Tank 1982–1992'', nearly double the original protection of the Abrams.<ref name="Zaloga_Sarson_11" /> In ''M1 Abrams vs T-72 Ural'', he uses different estimates of {{convert|600|mm|abbr=on}} vs APFSDS and {{convert|700|mm|abbr=on}} vs HEAT for the front hull and {{convert|800|mm|abbr=on}} vs APFSDS and {{convert|1300|mm|abbr=on}} vs HEAT for the front of the turret.<ref name="T-72vsM1" /> The protection of M1A2 SEP is a frontal turret armor estimate of {{convert|940-960|mm|abbr=on}} vs APFSDS and {{convert|1320-1620|mm|abbr=on}} vs HEAT, glacis estimate of {{convert|560-590|mm|abbr=on}} vs APFSDS and {{convert|510-1050|mm|abbr=on}} vs HEAT, and lower front hull estimate of {{convert|580-650|mm|abbr=on}} vs APFSDS and {{convert|800-970|mm|abbr=on}} vs HEAT. The M1A2 SEPv3 increased the LOS thickness of the turret and hull front armor; total armor protection from this increase is not known.<ref name=autogenerated1/>

In 1998, a program was begun to incorporate improved hull, turret, and side armor into the M1A2. This was intended to offer better protection against rocket-propelled grenades that were more modern than the baseline RPG-7. These kits were installed on about 325 older M1A2 tanks in 2001–2009 and were also included in upgraded tanks.{{sfn|Zaloga|Sarson|1993|p=48}}

[[File:Abrams XM32 tile installation.jpg|thumb|right|A U.S. Army M1A1 with XM32 tiles instead of XM19 reactive armor in 2017]]
The Abrams may also be fitted with explosive [[reactive armor]] over the track skirts if needed (such as the Tank Urban Survival Kit)<ref name=Army_TUSK_upgrades/> and [[slat armor]] over the rear of the tank and rear fuel cells to protect against [[Anti-tank missile|ATGMs]].

The 105&nbsp;mm M1 Abrams does not use [[spall liner]]s, though three 105&nbsp;mm rounds on the turret basket floor are covered with [[spall]] protection covers on the M1 tank variant.<ref>{{cite book |last1=Green |first1=Michael |title=M1 Abrams Main Battle Tank: The Combat and Development History of the General Dynamics M1 and M1A1 Tanks |date=1992 |publisher=Motorbooks International |isbn=0-87938-597-9 |pages=42, 67 |url=https://archive.org/details/m1abramsmainbatt0000gree/page/66/mode/2up?q=spall |access-date=28 December 2023}}</ref>

====Damage control====
The tank has a [[gaseous fire suppression|halon firefighting]] system to automatically extinguish fires in the crew compartment. The engine compartment has a firefighting system that is engaged by pulling a T-handle located on the left side of the hull. The Halon gas can be dangerous to the crew.<ref>{{cite web |url=https://www.cdc.gov/niosh/npg/npgd0634.html |title=NIOSH Pocket Guide to Chemical Hazards |publisher=CDC |url-status=live |archive-url=https://web.archive.org/web/20170818091459/https://www.cdc.gov/niosh/npg/npgd0634.html |archive-date=18 August 2017}}</ref> However, the toxicity of [[Halon 1301]] gas at 7% concentration is much lower than the combustion products produced by fire in the crew compartment, and CO<sub>2</sub> dump would be lethal to the crew.<ref name="The_Chieftain">{{Citation|last=The_Chieftain|title=Chieftain Chats Abrams|date=14 October 2018 |url=https://www.youtube.com/watch?v=aladW_D4nKU|access-date=21 February 2019|archive-date=14 October 2018|archive-url=https://web.archive.org/web/20181014180752/https://www.youtube.com/watch?v=aladW_D4nKU&gl=US&hl=en |url-status=live}}</ref>

The crew compartment also contains small hand-held [[fire extinguisher]]s. Fuel and ammunition are stored in armored compartments with [[blowout panel]]s intended to protect the crew from the risk of the tank's own ammunition [[cooking off]] (exploding) if the tank is damaged. The main gun's ammunition is stored in the rear section of the turret, with blast doors that open under power by sliding sideways only to remove a round for firing, then automatically close. Doctrine mandates that the ammunition door must be closed before arming the main gun.<ref name="The_Chieftain"/>

====NBC protection====
Starting with the M1A1 variant [[CBRN defense|nuclear, biological, chemical]] protection was provided by a turret [[Overpressure (CBRN protection)|overpressure]] system. Previously the Abrams crew had been required to don [[NBC suit]]s in case of an NBC attack. NBC masks are still retained as a backup, and crews often train while wearing them to remain proficient and combat-effective in such a scenario.<ref name="M1 Tank Story">{{cite news |last1=Lett |first1=Philip W. |title=The M1 Tank Story |work=Marine Corps Gazette |agency=U.S Marine Corps |issue=August 1991}}</ref>

====Tank Urban Survival Kit====
[[File:OCPA-2005-03-09-165522.jpg|thumb|left|An M1A2 with TUSK]]

The Tank Urban Survival Kit (TUSK) is a series of improvements to the M1 Abrams intended to improve fighting ability in urban environments.<ref name=Army_TUSK_upgrades>{{cite web |url=https://www.army.mil/article/7495/modified-m1-a2-abrams-tanks-improve-safety-precision |title=Modified M1-A2 Abrams Tanks Improve Safety, Precision |date=19 February 2008 |access-date=22 July 2017 |url-status=live |archive-url=https://web.archive.org/web/20130515232734/http://www.army.mil/article/7495/modified-m1-a2-abrams-tanks-improve-safety-precision |archive-date=15 May 2013}}</ref> Historically, urban and other close battlefields have been poor places for tanks to fight. A tank's front armor is much stronger than that on the sides, top, or rear. In an urban environment, attacks can come from any direction, and attackers can get close enough to reliably hit weak points in the tank's armor or gain sufficient elevation to hit the top armor.

Armor upgrades include reactive armor on the sides of the tank and [[slat armor]] on the rear to protect against [[rocket-propelled grenade]]s and other shaped charge warheads.{{sfn|Green|Stewart|2005|p=93}} Abrams Reactive Armor Tile (ARAT) I consists of 32 XM19 reactive armor boxes added to the sides of the tank. ARAT II consists of rounded XM32 reactive armor tiles mounted over-top the XM19 tiles.{{sfn|Zaloga|2019|p=24-25}} A [[Transparent Armor Gun Shield]] and a thermal sight system are added to the loader's top-mounted M240B 7.62&nbsp;mm machine gun,{{sfn|Zaloga|2019|p=24-25}} and a [[Kongsberg Gruppen]] Remote Weapon Turret carrying a 12.7&nbsp;mm (.50 in) caliber machine gun (again similar to that used on the Stryker) is in place of the tank commander's original 12.7&nbsp;mm (.50 in) caliber machine gun mount, wherein the commander had to expose himself to fire the weapon manually. An exterior [[telephone]] allows supporting infantry to communicate with the tank commander.{{sfn|Zaloga|2019|p=24-25}}

[[File:M1A1 Abrams with Integrated Management System new Tank Urban Survivability Kit Dec. 2007.jpg|thumb|An M1A1 Abrams with an Abrams Integrated Management System (AIM) and the Tank Urban Survivability Kit (TUSK) conducting a patrol in Baghdad, 2007.]]
In August 2006, General Dynamics Land Systems received a U.S. Army order for 505 Tank Urban Survivability Kits (TUSK) for Abrams main battle tanks supporting operations in Iraq, under a US$45&nbsp;million contract. Deliveries were expected to be completed by April 2009.<ref name="TUSK_def_update">{{cite web |url=http://defense-update.com/products/t/tusk.htm|title=Tank Urban Survivability Kit (TUSK)|access-date=11 October 2014 |url-status=dead|archive-url=https://web.archive.org/web/20141013121147/http://defense-update.com/products/t/tusk.htm |archive-date=13 October 2014}}</ref> Under a separate order, the U.S. Army awarded General Dynamics Armament and Technical Products (GDATP) US$30 million to produce reactive armor kits to equip M1A2s.<ref name="TUSK_def_update" />

Tiles will be produced at the company's reactive armor facility in Stone County Operations, [[McHenry, Mississippi]]. In December 2006, the U.S. Army added Counter Improvised Explosive Device enhancements to the M1A1 and M1A2 TUSK, awarding GDLS $11.3&nbsp;million contract, part of the $59&nbsp;million package mentioned above. In December, GDLS also received an order, amounting to around 40% of a US$48&nbsp;million order, for loader's thermal weapon sights being part of the TUSK system improvements for the M1A1 and M1A2 Abrams Tanks.<ref name="TUSK_def_update" />

====Active protection system====
In addition to the armor, some USMC Abrams tanks were equipped with a [[Active protection system#Soft-kill measures|soft-kill active protection system]], the AN/VLQ-6 Missile Countermeasure Device (MCD) that can impede the function of guidance systems of some semi-active control line-of-sight ([[SACLOS]]) [[wire-guided missile|wire]]- and [[command guidance|radio guided]] anti-tank missiles (such as the Russian [[9K114 Shturm]]) and [[infrared homing]] missiles. These were not ready in time for the Gulf War. The MCD works by emitting a massive, condensed infrared signal to confuse the infrared homing seeker of an [[anti-tank guided missile]] (ATGM). However, the drawback to the system is that the ATGM is not destroyed, it is merely directed away from its intended target, leaving the missile to detonate elsewhere.<ref name="ActiveDefenseCountermeasures">{{cite web |url=http://www.defense-update.com/features/du-1-04/soft-kill-west.htm |title= Active Defense & Countermeasures |publisher=Defense Update.com |date=25 April 2006 |access-date=9 June 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090310041758/http://www.defense-update.com/features/du-1-04/soft-kill-west.htm |archive-date=10 March 2009}}</ref> During the Iraq War the U.S. Marine Corps equipped its M1A1s with AN/VLQ-8A electro-optical jammers.{{sfn|Green|Stewart|2005|p=107-108}}

[[File:M1A1 Trophy Technology Demonstrator.jpg|thumb|The Trophy Active Protection System (APS) was installed and tested on a USMC M1A1 Abrams in 2017.]]
In 2016, the U.S. Army and Marine Corps began testing the Israeli [[Trophy (countermeasure)|Trophy]] active protection system to protect their Abrams tanks from modern RPG and ATGM threats by either jamming (with ATGMs) or firing small rounds to deflect incoming projectiles.<ref>[https://news.usni.org/2016/04/14/walsh-marines-may-protect-tanks-with-active-and-ew-protection-systems-much-like-ship-self-defense Walsh: Marines May Protect Tanks With Active and EW Protection Systems, Much Like Ship Self-Defense] {{webarchive |url=https://web.archive.org/web/20160414131211/https://news.usni.org/2016/04/14/walsh-marines-may-protect-tanks-with-active-and-ew-protection-systems-much-like-ship-self-defense |date=14 April 2016}} – News.USNI.org, 14 April 2016</ref> The Army planned to field a brigade of over 80 tanks equipped with Trophy to Europe in 2020.<ref>[http://www.military.com/daily-news/2017/10/09/some-abrams-tanks-trophy-system-2020-army.html?ESRC=todayinmil.sm Some Abrams Tanks Will Have "Trophy" System By 2020: Army] {{Webarchive |url=https://web.archive.org/web/20171011022416/http://www.military.com/daily-news/2017/10/09/some-abrams-tanks-trophy-system-2020-army.html?ESRC=todayinmil.sm |date=11 October 2017}} – Military.com, 9 October 2017</ref> It is planned for up to 261 Abrams to be upgraded with the system, enough for four brigades.<ref>[https://breakingdefense.com/2018/05/all-armored-brigades-to-get-active-protection-systems-gen-milley/ All Armored Brigades To Get Active Protection Systems: Gen. Milley] {{Webarchive |url=https://web.archive.org/web/20180715011501/https://breakingdefense.com/2018/05/all-armored-brigades-to-get-active-protection-systems-gen-milley/ |date=15 July 2018}}. ''Breaking Defense''. 15 May 2018.</ref> In June 2018, the Army awarded [[Leonardo DRS]], U.S. partner to Trophy's designer [[Rafael Advanced Defense Systems|Rafael]], a $193 million contract to deliver the system in support of M1 Abrams "immediate operational requirements".<ref>[https://www.armytimes.com/news/2018/07/05/abrams-tanks-get-new-round-of-israeli-made-shields-to-fend-off-anti-tank-weapons/ Abrams tanks get new round of Israeli-made "shields" to fend off anti-tank weapons] {{Webarchive |url=https://web.archive.org/web/20230114043747/https://www.armytimes.com/news/2018/07/05/abrams-tanks-get-new-round-of-israeli-made-shields-to-fend-off-anti-tank-weapons/ |date=14 January 2023}}. ''Army Times''. 6 July 2018.</ref> U.S. Army M1A2 SEPv2 Abrams tanks deployed to Germany in July 2020 fitted with Trophy systems.{{cn|date=April 2025}} Deliveries to equip four tank brigades were completed in January 2021.<ref>[https://breakingdefense.com/2021/01/army-tries-again-to-protect-stryker-rafael-or-rheinmetall/ Army Tries (Again) To Protect Stryker: Rafael or Rheinmetall?] {{Webarchive |url=https://web.archive.org/web/20210111054635/https://breakingdefense.com/2021/01/army-tries-again-to-protect-stryker-rafael-or-rheinmetall/ |date=11 January 2021}}. ''Breaking Defense''. 8 January 2021.</ref>

===Armament===

====Primary====

====M68A1 rifled gun====
[[File:XM1 Abrams interior.jpg|thumb|right|XM1 interior]]
[[File:U.S Army M1 Abrams 105 mm rounds laid out Desert Shield.jpg|thumb|right|105&nbsp;mm [[APFSDS]] rounds are laid out in Operation Desert Shield, 1991]]

The main armament of the original model M1 and IPM1 was the M68A1 105&nbsp;mm rifled tank gun firing a variety of [[Armour-piercing fin-stabilized discarding sabot|APFSDS]], [[High-explosive anti-tank|HEAT]], high explosive, [[white phosphorus]] rounds and an [[anti-personnel]] (multiple [[flechette]]) round. This gun used a license-made tube of the British [[Royal Ordnance L7]] gun together with the vertical sliding breech block and other parts of the U.S. T254E2 prototype gun. However, a longer ranged weapon was always envisaged, with lethality beyond {{convert|3|km|adj=on|sp=us|order=flip}} to combat newer armor technologies. To attain that lethality, the projectile diameter needed to be increased. The tank was able to carry 55 105&nbsp;mm rounds, with 44 stored in the turret blowout compartment and the rest in hull stowage.

Being non-combustible, the empty cartridge cases of the M1 variant accumulated on the turret floor after firing. After allowing some time to cool, they were ejected out of the hatch by the loader.{{sfn|Green|Stewart|2005|p=62-65}}

====M256 smoothbore gun====
The main armament of the M1A1 and M1A2 is the M256 120&nbsp;mm smoothbore gun, designed by Rheinmetall AG of Germany, manufactured under license in the U.S. by [[Watervliet Arsenal]], New York. The M256 is an improved variant of the [[Rheinmetall 120&nbsp;mm gun|Rheinmetall 120&nbsp;mm L/44 gun]] carried on the German [[Leopard 2]] on all variants up to the Leopard 2A5, the difference being in thickness and chamber pressure. Leopard 2A6 replaced the L/44 barrel with a longer L/55. Due to the increased caliber, only 40 or 42 rounds are able to be stored depending on if the tank is an A1 or A2 model.
* Elevation: −9 to +20 degree

[[File:US Army M1 Abrams exercise.ogv|thumb|left|M1 Abrams during a U.S. Army firing exercise, displaying internal crew cabin operations.]]
[[File:M1 Abrams turret fire above.jpg|thumb|left|An M1A1 firing its main gun as seen from the loader's hatch in joint exercises with the [[French Foreign Legion]].]]
The M256 fires ammunition with combustible cartridge cases made out of [[nitrocellulose]]. The cartridges were safer against premature ignition and flarebacks than earlier combustible cartridge rounds, but not entirely accident-proof.{{sfn|Green|Stewart|2005|p=62-65}}
The M256 fires a variety of rounds. The primary APFSDS round of the Abrams is the depleted uranium [[M829]] round, of which four variants have been designed. [[M829#M829A1|M829A1]], known as the "Silver Bullet", saw widespread service in the Gulf War, where it proved itself against Iraqi armor such as the T-72. The [[M829#M829A2|M829A2]] APFSDS round was developed specifically as an immediate solution to address the improved protection of a Russian [[T-72]], [[T-80]]U or [[T-90]] main battle tank equipped with [[Kontakt-5]] explosive reactive armor (ERA).<ref name=autogenerated1/>

Later, the [[M829#M829A3|M829A3]] round was introduced in 2002 to improve its effectiveness against next-generation ERA equipped tanks.{{sfn|Green|Stewart|2005|p=70}} Development of the [[M829]] series is continuing with the [[M829#M829A4|M829A4]] currently entering production, featuring advanced technology such as data-link capability.<ref>{{cite web|title=Next-Gen 120&nbsp;mm Tank Killer: ATK's M829E4 AKE |url=http://www.defenseindustrydaily.com/Next-Gen-120mm-Tank-Killer-ATKs-M829E4-AKE-06995/|publisher=Defense Industry Daily |url-status=live|archive-url=https://web.archive.org/web/20110716123723/http://www.defenseindustrydaily.com/Next-Gen-120mm-Tank-Killer-ATKs-M829E4-AKE-06995/|archive-date=16 July 2011}}</ref>

The Abrams also fires HEAT warhead shaped charge rounds such as the [[M830]], the latest version of which ([[M830#M830A1 HEAT MP-T|M830A1]]) incorporates a sophisticated multi-mode electronic sensing [[Fuse (explosives)|fuse]] and more fragmentation that allows it to be used effectively against armored vehicles, personnel, and low-flying aircraft. The Abrams uses a manual loader, who also provides additional support for maintenance, observation post/listening post (OP/LP) operations, and other tasks.

The new M1028 120&nbsp;mm anti-personnel [[Canister shot|canister]] cartridge was brought into service early for use in the [[Timeline of the Iraq War#2003|aftermath of the 2003 invasion of Iraq]]. It contains 1,098 {{convert|3/8|in|adj=on}} tungsten balls that spread from the muzzle to produce a [[shotgun]] effect lethal out to {{convert|600|m|sp=us}}. The tungsten balls can be used to clear enemy dismounts, break up hasty ambush sites in urban areas, clear [[defile (geography)|defiles]], stop infantry attacks and counter-attacks and support friendly infantry assaults by providing covering fire. The canister round is also a highly effective breaching round and can level cinder block walls and knock man-sized holes in reinforced concrete walls for infantry raids at distances up to {{convert|75|m|sp=us}}.<ref>{{cite journal |last=Hilmes |first=Rolf |date=1 December 2004 |page=79 |title=Arming Future MBTs&nbsp;– Some Considerations |journal=Military Technology |publisher=Mönsch}}</ref>

Also in use is the M908 obstacle-reduction round. It is designed to destroy obstacles and barriers. The round is a modified [[M830#M830A1|M830A1]] with the front fuse replaced by a steel nose to penetrate into the obstacle before detonation.<ref>[http://www.atk.com/products-services/m908-he-or-t-ammunition-120-mm-2/ "M908 HE-OR-T"] {{webarchive |url=https://web.archive.org/web/20141112033858/http://www.atk.com/products-services/m908-he-or-t-ammunition-120-mm-2/ |date=12 November 2014}}. ATK.com</ref>

The U.S. Army Research Laboratory (ARL) conducted a thermal analysis of the M256 from 2002 to 2003 to evaluate the potential of using a hybrid barrel system that would allow for multiple weapon systems such as the XM1111 Mid-Range munition, airburst rounds, or [[M1147 Advanced Multi-Purpose|XM1147]]. The test concluded that mesh density (number of elements per unit area) impacts accuracy of the M256 and specific densities would be needed for each weapon system.<ref>{{cite report |last1=South |first1=Joseph T. |last2=Carter |first2=Robert H. |title=Thermal Analysis of an M256 120-mm Cannon |publisher=Defense Technical Information Center |publication-place=Fort Belvoir, VA |date=1 August 2005 |doi=10.21236/ada437279 |page=}}</ref>

In 2013, the Army was developing a new round to replace the [[M830]]/[[M830#M830A1|M830A1]], M1028, and M908. Called the [[M1147 Advanced Multi-Purpose|M1147]] Advanced Multi-Purpose [[M1147 Advanced Multi-Purpose|XM1147 Advanced Multi-Purpose]] (AMP) round, it will have point detonation, delay, and [[airburst round|airburst]] modes through an ammunition data-link and a multi-mode, programmable fuse in a single munition. Having one round that does the job of four would simplify logistics and be able to be used on a variety of targets. The AMP is to be effective against bunkers, infantry, light armor, and obstacles out to {{convert|500|m|abbr=on}}, and will be able to breach reinforced concrete walls and defeat [[ATGM]] teams from {{convert|500|to|2000|m|abbr=on}}.<ref>{{cite conference |url=http://www.dtic.mil/ndia/2012armaments/TuesdayPaulHill.pdf |conference=NDIA Joint Armaments Conference PM Panel|title=Advanced Multi Purpose (AMP) Overview and Status|last=Hill|first=Paul|date=May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121114131039/http://www.dtic.mil/ndia/2012armaments/TuesdayPaulHill.pdf|page=26 |archive-date=14 November 2012}}</ref><ref>[https://www.army.mil/article/98946/Army_developing_new_120mm_AMP_tank_round/ Army developing new 120&nbsp;mm AMP tank round]  – Army.mil, 19 March 2014</ref> [[Orbital ATK]] was awarded a contract to begin the first phase of development for the AMP [[M1147 Advanced Multi-Purpose|XM1147]] High-Explosive Multi-Purpose with Tracer cartridge in October 2015.<ref>[http://www.businesswire.com/news/home/20151008005038/en/Orbital-ATK-Awarded-16-Million-Develop-Generation Orbital ATK Awarded $16 Million to Develop Next Generation 120&nbsp;mm Tank Ammo] {{webarchive |url=https://web.archive.org/web/20151012025901/http://www.businesswire.com/news/home/20151008005038/en/Orbital-ATK-Awarded-16-Million-Develop-Generation |date=12 October 2015}} – Businesswire.com, 8 October 2015</ref> As of 2024 the round is undergoing the final testing stages, with the full-rate production decision scheduled for the end of the year.<ref>{{cite report |author1=Office of the Secretary of Defense |title=FY 2023 Annual Report - Director, Operational Test & Evaluation |date=January 2024 |pages=83–84 |url=https://www.dote.osd.mil/Portals/97/pub/reports/FY2023/other/2023annual-report.pdf |access-date=20 March 2024}}</ref>

In addition to these, the [[XM1111 Mid-Range Munition|XM1111]] (Mid-Range-Munition Chemical Energy) was also in development. The XM1111 was a guided munition using a dual-mode seeker that combined imaging-infrared and semi-active laser guidance. The MRM-CE was selected over the competing MRM-KE, which used a rocket-assisted kinetic energy penetrator. The CE variant was chosen due to its better effects against secondary targets, providing a more versatile weapon. The Army hoped to achieve IOC with the XM1111 by 2013.<ref>{{cite web|title=Clank Softly and Carry a Better Shillelagh |url=http://www.defenseindustrydaily.com/xm1111-clank-softly-and-carry-a-better-shillelagh-04544/|publisher=Defense Industry Daily |url-status=live|archive-url=https://web.archive.org/web/20110607011307/http://www.defenseindustrydaily.com/xm1111-clank-softly-and-carry-a-better-shillelagh-04544/|archive-date=7 June 2011}}</ref> However, the Mid-Range Munition was canceled in 2010 along with Future Combat Systems.{{sfn|Zaloga|2019|p=28}}

====Secondary====
[[File:M1 Abrams 1981 Gunner and Coax M240.jpg|thumb|right|A commander (left) and loader man their 12.7&nbsp;mm M2HB and 7.62&nbsp;mm M240 machine guns of their 105&nbsp;mm-armed M1 in 1981.]]

The Abrams tank has three machine guns, with an optional fourth:
# A .50 cal. ([[.50 BMG|12.7&nbsp;mm]]) [[M2 Browning|M2HB]] machine gun in front of the commander's hatch. On the M1 and M1A1, this gun is mounted on the Commander's Weapons Station. This allows the weapon to be aimed and fired from within the tank. Normal combat loadout for the M1A1 is a single 100-round box of ammo at the weapon, and another 900 rounds carried. The later M1A2 variant had a "flex" mount that required the tank commander to expose his or her upper torso in order to fire the weapon. In urban environments in Iraq this was found to be unsafe. With the Common Remote Operated Weapons System ([[CROWS]]) add-on kit, an M2A1 .50 Caliber Machine gun, M240, or [[M249 light machine gun|M249 SAW]] can be mounted on a CROWS remote weapons platform (similar to the [[Protector (RWS)|Protector M151]] remote weapon station used on the [[Stryker]] family of vehicles). Current variants of the Tank Urban Survival Kit (TUSK) on the M1A2 have forgone this,{{citation needed|date=December 2023}} instead adding transparent gun shields to the commander's weapon station.{{sfn|Zaloga|2019|p=24-25}} The upgrade variant called the M1A1 Abrams Integrated Management (AIM) equips the .50 caliber gun with a thermal sight for accurate night and other low-visibility shooting.<ref name="generaldynamics1">{{cite press release |url=http://generaldynamics.com/news/press_releases/2008/newsrelease%20september%205,%202008-3.htm |title=General Dynamics Awarded $34 Million for M1A1 Abrams Tank Upgrades |publisher=General Dynamics |date=5 September 2008 |archive-url=https://web.archive.org/web/20100103064632/http://generaldynamics.com/news/press_releases/2008/NewsRelease%20September%205%2C%202008-3.htm |archive-date=3 January 2010}}</ref>
# A [[7.62×51mm NATO|7.62&nbsp;mm]] [[M240 machine gun]] in front of the loader's hatch on a skate mount (seen at right). Some of these were fitted with [[gun shield]]s during the Iraq War, as well as night-vision scopes for low-visibility engagements and firing. This gun can be moved to the TC's position if the M2 .50 cal is damaged.
# A second 7.62&nbsp;mm M240 machine gun in a [[coaxial gun|coaxial]] mount (i.e., it points at the same targets as the main gun) to the right of the main gun. The coaxial MG is aimed and fired with the same computerized firing control system used for the main gun. On earlier M1 and M1A1s 3000 rounds are carried, all linked together and ready to fire. This was reduced slightly in later models to make room for new system electronics. A typical 7.62&nbsp;mm combat loadout is between 10,000 and 14,000 rounds carried on each tank.
# (Optional) A second coaxial .50 cal. (12.7&nbsp;mm) M2HB machine gun can be mounted directly above the main gun in a remote weapons platform as part of the CSAMM (Counter Sniper Anti Material Mount) package.

====Aiming====
[[File:DOD_108011149.webm|thumb|right|Locations of the gunner's sights and other components on a U.S. Army M1A2 Abrams (video)]]
[[File:M1A2 Abrams Thermal Sight.jpg|thumb|View through an M1A2 Abrams' thermal optic]]
The Abrams is equipped with a ballistic [[fire-control system|fire-control computer]] that uses user and system-supplied data from a variety of sources to compute, display, and incorporate the three components of a ballistic solution—lead angle, ammunition type, tube wear, propellant temperature, wind speed, air temperature, the relative motions of the target and the Abrams, and range to the target—to accurately fire the main gun.{{sfn|Green|Stewart|2005|p=77}} These three components are determined using a [[laser rangefinder]], crosswind sensor, a [[pendulum]] static cant sensor, data concerning performance and flight characteristics of each specific type of round, tank-specific boresight alignment data, ammunition temperature, air temperature, barometric pressure, a muzzle reference system (MRS) that determines and compensates for barrel drop at the muzzle due to gravitational pull and barrel heating due to firing or sunlight, and target speed determined by tracking rate tachometers in the Gunner's or Commander's Controls Handles.

All of these factors are computed into a ballistic solution and updated 30 times per second. The updated solution is displayed in the Gunner's or Tank Commander's field of view in the form of a reticle in both day and thermal modes.<ref name="M1A1 FCS">{{cite report |last1=Leu |first1=Michael |last2=Irwin |first2=Alan |last3=William |first3=Weil |last4=Jerome |first4=Hahn |title=Battlefield Management And Fire Control System for M1A1|date=15 February 1986 |pages=5–6, 5–11 |url=https://apps.dtic.mil/sti/pdfs/ADA182331.pdf |access-date=1 January 2024}}</ref> The ballistic computer manipulates the turret and a complex arrangement of mirrors so that all one has to do is keep the reticle on the target and fire to achieve a hit. Proper lead and gun tube elevation are applied to the turret by the computer, greatly simplifying the job of the gunner.{{Citation needed|date=August 2010}}

[[File:DA-SD-06-06814.jpg|thumb|left|A soldier assisting in the critical job of "boresighting" the alignment of all the tank's sights to the center of the axis of the bore of the main gun on an M1A1 Abrams in [[Mosul]], Iraq, in January 2005.{{refn|group=nb|name=Hand signals|Hand signals enable the gunner inside the tank to train the main gun onto a boresighting target.}}]]
The fire control system on the M1 and M1A1 variants is the [[Computing Devices Canada]] ballistic computer system.{{sfn|Cullen|Foss|1997|p=343}} On the M1A2 the Fire Control Electronics Unit is manufactured by GDLS.<ref>{{cite news |last1=Hammick |first1=Murray |title=Abrams M1A2 |work=International Defense Review |issue=9 |publisher=Jane's Information Group |date=1990 |location=Surrey |page=1045}}</ref> The laser designator is a [[Hughes Aircraft Company|Hughes]] model.{{sfn|Cullen|Foss|1997|p=447}} This fire control system uses this data to compute a [[firing solution]] for the gunner. The ballistic solution generated ensures a hit percentage greater than 95&nbsp;percent at nominal ranges.{{Citation needed|date=August 2010}} Either the commander or gunner can fire the main gun. Additionally, the Commander's Independent Thermal Viewer (CITV) on the M1A2 can be used to locate targets and pass them on for the gunner to engage while the commander scans for new targets.

If the primary sight system malfunctions or is damaged, the main and coaxial weapons can be manually aimed using a telescopic scope [[Boresight (firearm)|boresighted]] to the main gun known as the Gunner's Auxiliary Sight (GAS). The GAS has two interchangeable [[reticle]]s; one for HEAT and ''multi-purpose anti-tank'' (MPAT) ammunition and one for APFSDS and ''Smart Target-Activated Fire and Forget'' (STAFF) ammunition. Turret traverse and main gun elevation can be performed with manual handles and cranks if the ''fire control'' or ''hydraulic'' systems fail.

The commander's M2HB .50&nbsp;caliber machine gun on the M1 and M1A1 is aimed by a 3× magnification sight incorporated into the Commander's Weapon Station (CWS), while the M1A2 uses the machine gun's own [[iron sights]], or a remote aiming system such as the Common Remotely Operated Weapon Station (CROWS) system when used as part of the Tank Urban Survival Kit. The loader's M240 machine gun is aimed either with the built-in iron sights or with a thermal scope mounted on the machine gun.{{Citation needed|date=August 2010}}

[[File:The Abrams Integrated Display and Targeting System, or AIDATS,.jpg|thumb|Abrams Integrated Display and Targeting System (AIDATS) on a USMC M1A1.]]
In late 2017, the 400 USMC M1A1 Abrams were to be upgraded with better and longer-range sights on the Abrams Integrated Display and Targeting System (AIDATS) replacing the black-and-white camera view with a color sight and day/night thermal sight, simplified handling with a single set of controls, and a slew to cue button that repositions the turret with one command. Preliminary testing showed the upgrades reduced target engagement time from six seconds to three by allowing the commander and gunner to work more closely and collaborate better on target acquisition.<ref>[http://www.dodbuzz.com/2016/08/23/abrams-tank-upgrades-will-give-marines-killer-edge/ Abrams Tank Upgrades Will Give Marines 'Killer Edge'] {{webarchive |url=https://web.archive.org/web/20160824062936/http://www.dodbuzz.com/2016/08/23/abrams-tank-upgrades-will-give-marines-killer-edge/ |date=24 August 2016}} – DoDBuzz.com, 23 August 2016</ref><ref>[https://www.marinecorpstimes.com/articles/marines-m1a1-tanks-are-about-to-get-even-more-awesome Marines' M1A1 tanks: How an upgrade will help make them more lethal] {{webarchive |url=https://web.archive.org/web/20160827201232/https://www.marinecorpstimes.com/articles/marines-m1a1-tanks-are-about-to-get-even-more-awesome |date=27 August 2016}} – MarineCorpstimes.com, 26 August 2016</ref>

===Mobility===

====Tactical====
[[File:AGT1500 engine and M1 tank.JPEG|thumb|Marines from 1st Tank Battalion load a [[Honeywell AGT1500]] multifuel turbine back into a tank at Camp Coyote, Kuwait, February 2003.]]
{{see also|AGT1500}}

The M1 Abrams's [[powertrain]] consists of an AGT1500 [[multifuel]] gas turbine (originally made by [[Lycoming Engines|Lycoming]], now [[Honeywell]]) capable of {{convert|1500|shp|kW|sp=us}} at 30,000 [[Revolutions per minute|rpm]] and {{convert|395|lb·ft|Nm|abbr=on}} at 10,000 rpm and a six-speed (four forward, two reverse) [[Allison Transmission|Allison]] X-1100-3B Hydro-Kinetic [[automatic transmission]]. This gives it a governed top speed of {{convert|45|mph|km/h|abbr=on}} on paved roads, and {{convert|30|mph|km/h|abbr=on}} cross-country. With the engine governor removed, speeds of around {{convert|60|mph|km/h|abbr=on}} are possible on an improved surface. However, damage to the drivetrain (especially to the tracks) and an increased risk of injuries to the crew can occur at speeds above {{convert|45|mph|km/h|0|abbr=on}}.

The tank was built around this engine and it is multifuel-capable, including diesel, gasoline, [[marine diesel oil|marine diesel]] and [[jet fuel]] (such as [[JP-4]] or [[JP-8]]).<ref>{{Cite web |url=http://www.honeywell.com/sites/aero/Turboprops3_CDF1BA7AE-8A37-9A78-EC1A-E00A4B74F3E9_H52422376-8368-1EC3-AA6D-83165D399CBF.htm |title=Honeywell Aerospace – AGT1500 |access-date=21 January 2023 |archive-date=8 March 2008 |archive-url=https://web.archive.org/web/20080308153949/http://www.honeywell.com/sites/aero/Turboprops3_CDF1BA7AE-8A37-9A78-EC1A-E00A4B74F3E9_H52422376-8368-1EC3-AA6D-83165D399CBF.htm |url-status=dead}}</ref><ref>{{cite web |url=http://www.accessmylibrary.com/coms2/summary_0286-17629659_ITM |title=Heavy duty: overhaul under way for Abrams tank engine |publisher=Accessmylibrary.com |date= 1 September 2006 |access-date= 9 June 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090111230441/http://www.accessmylibrary.com/coms2/summary_0286-17629659_ITM |archive-date=11 January 2009}}</ref><ref>{{cite news |last1=Roblin |first1=Sebastien |title=The US's powerful Abrams tanks are heading to Ukraine, but generals disagree over how hard it'll be to use them on the battlefield |url=https://www.businessinsider.com/generals-disagree-on-difficulty-of-using-abrams-tanks-for-ukraine-2023-2 |work=Business Insider |agency=19fortyfive |publisher=Insider |date= 1 February 2023 |access-date= 2 April 2025}}</ref> In the AGT1500, jet fuel has poorer fuel economy and operating range compared to diesel. By 1989, the Army was transitioning solely to JP-8 for the M1 Abrams, part of a plan to reduce the service's [[logistics]] burden by using a single fuel for aviation and ground vehicles.<ref>{{cite news |last1=Evans |first1=David |title=Tanks Running on Poor Ideas and Bad Planning |url=https://www.chicagotribune.com/news/ct-xpm-1989-09-01-8901090654-story.html |access-date=21 January 2023 |work=Chicago Tribune |publisher=Tribune Publishing |date=1 September 1989}}</ref> The Australian M1A1 AIM SA burns diesel fuel, since the use of JP-8 is less common in the Australian Army.{{citation needed|date=March 2023}}

[[File:M1a1 drivers hole.jpg|thumb|left|M1A1 driving controls]]
[[File:M1A1 auxiliary power unit Saudi Arabia.jpg|thumb|left|An American M1A1 fitted with an external [[auxiliary power unit]] in Operation Desert Storm.]]
The gas turbine propulsion system has proven quite reliable in practice and combat, but its high fuel consumption is a serious logistic problem.<ref name=autogenerated1/> It burns between 1.5 and 3 gallons per mile.<ref>{{Cite news |last=Jon |first=Jackson |date=2023-01-25 |title=Game-changing Abrams tanks present one glaring problem for Ukraine |url=https://www.newsweek.com/us-abrams-tanks-fueling-problems-ukraine-1776639 |access-date=2024-09-10 |publisher=[[Newsweek]] |language=en}}</ref>

The turbine is very quiet when compared to diesel engines of similar power output and produces a high-pitched whine, reducing the audible distance of the sound, thus earning the Abrams the nickname "whispering death" during its worldwide debut at the 1982 [[Reforger]] exercise.{{sfn|Kelly|1989|p=267}}<ref name=Grummitt>{{cite book |last1=Grummitt |first1=David |title=M1 Abrams: The U.S's Main Battle Tank in American and Foreign Service, 1981–2019 |year=2019 |publisher=Pen & Sword |location=South Yorkshire |isbn=978-1-526749772 |url=https://books.google.com/books?id=hOMSEAAAQBAJ&dq=%22whispering+death%22+reforger&pg=PT37 |access-date=8 January 2024}}</ref>

By the time production of the AGT1500 ended in 1994, the U.S. had purchased 12,000 such engines. In 2006 the Army awarded Honeywell a contract to overhaul 1000 engines, with options for up to 3000 more.<ref>{{cite news |title=Overhaul under way for Abrams tank engine |url=https://www.nationaldefensemagazine.org/articles/2006/9/1/2006september--overhaul-under-way-for-abrams-tank-engine |access-date=5 June 2024 |work=www.nationaldefensemagazine.org |date=1 September 2006}}</ref>

The Army received proposals, including two diesel options, to provide the common engine for the [[XM2001 Crusader]] and Abrams. In 2000, the Army selected the gas turbine engine LV100-5 from Honeywell and subcontractor [[General Electric]].<ref name="Honeywell selected">{{cite news |last1=Dupont |first1=Daniel G. |title=Tanks Won't Be Converted to Diesel: Honeywell Turbine Engine Picked for Abrams Fleet, Crusader System |url=https://www.jstor.org/stable/43985032 |access-date=7 February 2022 |work=Inside the Army |issue=38 |publisher=Inside Washington Publishers |date=25 September 2000 |volume=12 |pages=1, 11 |jstor=43985032 |archive-date=7 February 2022 |archive-url=https://web.archive.org/web/20220207070455/https://www.jstor.org/stable/43985032 |url-status=live}}</ref> The new LV100-5 engine was smaller (43% fewer parts) with rapid acceleration, quieter running, and no visible exhaust.<ref>{{cite web |url=http://www.geae.com/engines/military/lv100/index.html |title=GE – Aviation: LV100 |access-date=7 August 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080607052044/http://www.geae.com/engines/military/lv100/index.html |archive-date=7 June 2008}}</ref> It also featured a 33% reduction in fuel consumption (50% less when idle) and near drop-in replacement.<ref>{{cite web |url=http://www.geae.com/engines/military/lv100/spotlight_advantages.html |title=GE – Aviation: LV100 Advantages |access-date=7 August 2008 |url-status=dead|archive-url=https://web.archive.org/web/20080618180930/http://www.geae.com/engines/military/lv100/spotlight_advantages.html |archive-date=18 June 2008}}</ref> The Common Engine Program was shelved when the Crusader program was canceled. Phase 2 of Army's PROSE (Partnership for Reduced O&S Costs, Engine) program, however, called for further development of the LV100-5 and replacement of the current AGT1500 engine.<ref>{{cite web |url=http://www.defenseindustrydaily.com/aim-programs-m1a1-tank-refits-and-rebuilds-continue-0440/ |title=AIM Program's M1A1 Tank Refits and Rebuilds Continue |publisher=Defenseindustrydaily.com |date=2 May 2005 |access-date=9 June 2009 |url-status=live |archive-url=https://web.archive.org/web/20090714194319/http://www.defenseindustrydaily.com/aim-programs-m1a1-tank-refits-and-rebuilds-continue-0440/ |archive-date=14 July 2009}}</ref>

[[File:US Navy 031214-N-3236B-008 A Marine from the 13th Marine Expeditionary Unit (13th MEU) Tank Platoon BLT 1-1 stationed at Twentynine Palms, Calif., directs an M1-A1 Abrams tank during a training exercise.jpg|thumb|A U.S. Marine M1A1 fitted with snorkel attachment and [[bustle rack]] extension.]]
From 1991 to 1994, the Army fitted 1,500 Abrams turrets with external [[auxiliary power unit]]s (APU). APUs allow some the Abrams to run some functions without running on the engine. Some Abrams tanks that saw service during the Gulf War were fitted with such a device.{{sfn|Zaloga|2009|p=20}} Although the Army favored an under-armor APU, Congress instead funded a short-term modification to 336 M1A2 Abrams. These were installed in 1997.{{sfn|Zaloga|2009|p=19}} An under-armor APU located in the hull was chosen for the M1A2 SEP variant. When this proved unreliable, it was replaced with a battery-based Alternate APU starting in 2005.{{sfn|Zaloga|2009|p=20}}

[[File:White Falcons Integrate Armor Support for Combined Arms Live Fire Exercise in New Mexico 150930-A-DP764-009.jpg|thumb|[[82nd Airborne Division|82nd Airborne]] [[paratrooper]]s ride on an M1 Abrams by [[tank desant]].]]
Although the M1 tank is not designed to carry riders easily, provisions exist for the Abrams to transport troops in [[tank desant]] with the turret stabilization device switched off. A battle-equipped infantry squad may ride on the rear of the tank, behind the turret. The soldiers can use ropes and equipment straps to provide handholds and snap links to secure themselves.<ref name="passenger">{{cite book |title=U.S. Army Warrior Ethos And Combat Skills Handbook (Field Manual No. 3‑21.75) |year=2009 |publisher=Morris Book Publishing, LLC |isbn=978-1-59921-819-9 |url=https://rdl.train.army.mil/soldierPortal/atia/adlsc/view/public/24572-1/FM/3-21.75/ |chapter-url=https://rdl.train.army.mil/soldierPortal/atia/adlsc/view/public/24572-1/FM/3-21.75/chap7.htm |author=Department of the Army |access-date=2 June 2010 |chapter=7 |url-status=dead |archive-url=https://web.archive.org/web/20110720003542/https://rdl.train.army.mil/soldierPortal/atia/adlsc/view/public/24572-1/FM/3-21.75/ |archive-date=20 July 2011}}</ref><!-- A statement about how often this is actually used would be good, if a source is available for that, thanks. -->

The Abrams T156 is a permanently bonded rubber track pad, a distinctive feature not found on any other tank. Unlike other tanks with replaceable track pads, on the Abrams, a worn track pad is remedied by replacing the entire track shoe. The Abrams non-removable track pads save weight but are less desirable in snow as the pads cannot be replaced with [[grouser]]s.<ref>{{cite journal |last1=Williams |first1=Greg |title=The Army's M1 Tank: Has It Lived Up To Expectations? |journal=POGO |date=12 June 1990 |url=https://www.pogo.org/reports/armys-m1-tank-has-it-lived-up-to-expectations |access-date=27 December 2023}}</ref> As of 2007, M1 Abrams track wear constitutes the second-largest consumable expense in the U.S. Army, surpassed only by [[Meals, Ready to Eat]] consumption.<ref>{{cite journal |last1=Harris |first1=Lieutenant Colonel Benjamin |title=King of the Killing Zone: How Well Has It Held Up? |journal=Armor |issue=July–August 2007 |pages=18–20 |url=https://www.moore.army.mil/armor/eARMOR/content/issues/2007/JUL_AUG/ArmorJulyAugust2007web.pdf |archive-url=https://web.archive.org/web/20231227031845/https://www.moore.army.mil/armor/eARMOR/content/issues/2007/JUL_AUG/ArmorJulyAugust2007web.pdf |url-status=dead |archive-date=27 December 2023 |access-date=27 December 2023}}{{Source-attribution}}</ref> In 1988 the Army awarded [[FMC Corporation]] a contract for T158 tracks rated for {{convert|2100|miles}}, or about double the life of the previous shoe.{{sfn|Kelly|1989|pp=244–245}} These feature replaceable pads and are about 3000 pounds heavier.{{sfn|Hunnicutt|2015|p=248-249}} The driver is equipped with a thermal viewer. On at least some models this is the Hughes AN/VAS-3.{{sfn|Cullen|Foss|1997|p=424}}

====Strategic====
[[File:DF-SD-06-12692.jpg|thumb|A U.S. Army M1A1 after being offloaded from a U.S. Air Force [[C-17 Globemaster III|C-17]] at [[Balad Air Base]], Iraq in 2004]]
[[File:M1 strategic mobility.jpg|thumb|A Marine M1A1 offloading from a [[Landing Craft Air Cushioned]] vehicle]]

Strategic mobility is the ability of the tanks of an armed force to arrive in a timely, cost effective, and synchronized fashion. The Abrams can be carried by a [[C-5 Galaxy]] or a [[C-17 Globemaster III]]. The limited capacity (two combat-ready tanks in a C-5, one combat-ready tank in a C-17) caused serious logistical problems when deploying the tanks for the first Gulf War, though there was enough time for 1,848 tanks to be transported by ship.

The Marines transported their [[Marine Air-Ground Task Force]] Abrams tanks by combat ship. A ''[[Wasp class amphibious assault ship|Wasp]]''-class [[Landing Helicopter Dock]] (LHD) typically carried a platoon of four to five tanks attached to the deployed [[Marine Expeditionary Unit]], which were then amphibiously transported to shore by [[Landing Craft Air Cushion]] (LCAC) at one combat-ready tank per landing craft.

The Abrams is also transportable by truck, namely the [[Oshkosh M1070]] and M1000 [[Heavy Equipment Transporter System]] (HETS) for the US Military. The HETS can operate on highways, secondary roads, and cross-country. It accommodates the four tank crew members.<ref>{{cite web |url=http://www.army.mil/factfiles/equipment/wheeled/m1070.html |title=M1070 Heavy Equipment Transporter (HET) Fact File United States Army |publisher=Army.mil |access-date=30 June 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100706020118/http://www.army.mil/factfiles/equipment/wheeled/m1070.html |archive-date=6 July 2010}}</ref> The Australian Army uses customized [[MAN SE|MAN]] trucks to transport its Abrams.<ref>{{cite news |title=Enter the Abrams |url=https://www.australiandefence.com.au/D4B755E0-F806-11DD-8DFE0050568C22C9 |access-date=31 August 2021 |work=Australian Defence Magazine |date=10 January 2008 |language=en |archive-date=31 August 2021 |archive-url=https://web.archive.org/web/20210831233756/https://www.australiandefence.com.au/D4B755E0-F806-11DD-8DFE0050568C22C9 |url-status=live}}</ref>

The first instance of the Abrams being airlifted directly into a battlefield occurred in October 1993. Following the [[Battle of Mogadishu (1993)|Battle of Mogadishu]], 18 M1 tanks were airlifted by C-5 aircraft to Somalia from [[Hunter Army Airfield]], Georgia.<ref>{{cite news |last=Haulman |first=Daniel L. |title=The United States Air Force In Somalia, 1992–1995 |url=http://www.dafhistory.af.mil/Portals/16/documents/Airmen-at-War/Haulman-USAFSomalia1992-1995.pdf?ver%3D2016-08-22-131410-337&usg=AFQjCNFCsGZTGkPjFg1zB2quBMa5EMKI-A |access-date=28 September 2017 |archive-url=https://web.archive.org/web/20170928193337/http://www.afhra.af.mil/Portals/16/documents/Airmen-at-War/Haulman-USAFSomalia1992-1995.pdf?ver%3D2016-08-22-131410-337&usg=AFQjCNFCsGZTGkPjFg1zB2quBMa5EMKI-A |archive-date=28 September 2017 |url-status=live}}</ref><ref>{{cite news |last=Leland |first=John W. |title=The Chronological History Of The C-5 Galaxy |url=https://www.amc.af.mil/Portals/12/documents/AFD-131018-052.pdf |work=? |access-date=29 September 2017 |archive-url=https://web.archive.org/web/20171010084126/http://www.amc.af.mil/Portals/12/documents/AFD-131018-052.pdf |archive-date=10 October 2017 |url-status=live}}</ref>

=== Issues ===

==== Air filter clog ====
In a NSIA report on the Abrams in the Gulf War, crews reported issues related to the turbine engine, other than the fuel consumption concerns, they noted the Abrams suffered from sand clogging the filters<ref>GAO. [https://www.gao.gov/assets/nsiad-92-94.pdf "Report to the Chairman, Subcommittee on Regulation, Business Opportunities, and Energy, Committee on Small Business, House of Representatives: OPERATION DESERT STORM Early Performance Assessment of Bradley and Abrams"]. U.S. General Accounting Office, January 1992. Accessed June 5, 2024.</ref> which were known to cause reduced fuel economy, or in the worst case, engine damage.