Editing M1 Abrams (section)

===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>