Editing M2 Browning (section)

===M2A1===
[[File:PEO M2E2-QCB HMG.jpg|thumb|M2E2 modification with quick-change barrel (QCB)]]

When the M2 was first being designed, John Browning faced two design challenges. With the machine tools available at that time, the dimensions that established the location of the bolt face and the depth of the chamber could not be held tightly enough to control the fit of the cartridge in the chamber. The round can be too tight in the chamber and the gun would not fire, or be too loose in the chamber, resulting in a stoppage or ruptured cartridge. The other dimension that could not be held closely enough was when the firing pin would fall. The solution to these problems was adjustable timing and headspace ("Timing" is the adjustment of the gun so that firing takes place when the recoiling parts are in the correct position for firing; "headspace" is the distance between the face of the bolt and the base of the cartridge case, fully seated in the chamber); the operator had to screw the barrel into the barrel extension, moving the barrel toward the bolt face to reach the proper headspace with simple gauges to allow the operator to adjust to the proper dimensions. By the late 20th century, the M2 was the only adjustable headspace weapon in the U.S. inventory. With rising reports of injuries from improperly headspaced weapons, the U.S. military held a competition for a quick change barrel conversion kit with fixed timing and headspace in 1997. Three companies offered kits and [[Saco Defense]] won the competition. However, funding was lost before the design could be fully evaluated and the program ended. In 2007, the military found money to start a new competition. Saco Defense had since been acquired by [[General Dynamics]], which won the competition.<ref>{{cite journal |url=http://sadefensejournal.com/wp/?p=428 |title=New .50 Cal Machine Guns, No Tanks |first=George |last=Kontis |date=19 August 2011 |journal=Small Arms Defense Journal |volume=1 |number=4 |url-status=dead |archive-url=https://web.archive.org/web/20131014190604/http://sadefensejournal.com/wp/?p=428 |archive-date=2013-10-14}}</ref>

[[File:RSOV at National War College April 19, 2001.JPEG|thumb|U.S. Army [[Ranger Special Operations Vehicle]] armed with RAMO M2HB-QCB machine gun]]
On 15 October 2010, the ''M2A1'' heavy machine gun was type classified by the U.S. Army. Formerly known as the M2E2, the M2A1 incorporates improvements to the design including a quick change barrel (QCB) with a removable carrying handle, a new slotted flash suppressor that reduces muzzle flash by 95 percent, fixed headspace and timing, a modified bolt, and a manual trigger block safety. When a standard M2 had a barrel change, the headspace and timing had to be manually set. Improper adjustment could damage the weapon and cause serious injury to the user. Fixed headspace and timing reduces risk, and the carrying handle allows the barrel to be switched in seconds.<ref>{{cite web |url=http://peosoldier.armylive.dodlive.mil/2011/01/03/M2a1/ |title=Ma Deuce version M2A1 - Proven Performer gets an Upgrade |first=D. |last=Dawson |date=3 January 2011 |website=PEOSoldier.mil |url-status=dead |archive-url=https://web.archive.org/web/20130219061002/http://peosoldier.armylive.dodlive.mil/2011/01/03/M2a1/ |archive-date=2013-02-19}}</ref><ref>{{cite web |url=http://www.defenseindustrydaily.com/ma-deuce-still-going-strong-03539/ |title=Ma Deuce Still Going Strong |date=1 November 2012 |website=Defense Industry Daily |url-status=dead |archive-url=https://web.archive.org/web/20130127084019/http://www.defenseindustrydaily.com/ma-deuce-still-going-strong-03539/ |archive-date=2013-01-27}}</ref> In June 2011, the Army began conversion of M2HB machine guns to M2A1s.<ref>{{cite web |url=http://www.thefirearmblog.com/blog/2011/08/06/army-to-convert-browning-M2-to-M2a1/ |title=Army to convert Browning M2 to M2A1 |date=6 August 2011 |website=The Firearm Blog |url-status=dead |archive-url=https://web.archive.org/web/20121114054200/http://www.thefirearmblog.com/blog/2011/08/06/army-to-convert-browning-M2-to-M2a1/ |archive-date=2012-11-14}}</ref> The M2A1 was named one of the greatest Army inventions of 2011.<ref>{{cite web |url=http://www.thefirearmblog.com/blog/2012/09/21/M2a1-among-greatest-army-inventions-of-2011/ |title=M2A1 Among Greatest Army Inventions of 2011 |date=21 September 2012 |website=The Firearm Blog |url-status=dead |archive-url=https://web.archive.org/web/20121127194519/http://www.thefirearmblog.com/blog/2012/09/21/M2a1-among-greatest-army-inventions-of-2011/ |archive-date=2012-11-27}}</ref> As of 30 November 2012, 8,300 built or converted M2A1s had been fielded by the U.S. Army; the program will upgrade the Army's entire M2 inventory of more than 54,000 guns.<ref>{{cite web |url=http://www.army.mil/article/92130/ |title=M2A1 Machine Gun Features Greater Safety, Heightened Lethality |first=Kevin |last=Doell |date=30 November 2012 |website=Army.mil |url-status=live |archive-url=https://web.archive.org/web/20131015043857/http://www.army.mil/article/92130/ |archive-date=2013-10-15}}</ref> The [[U.S. Marine Corps]] plans to upgrade all of their ground-mounted M2s to M2A1 standard from 2016 to 2018.<ref>{{cite news |url=http://www.marinecorpstimes.com/story/military/tech/2015/09/17/marines-unveil-plan-modernize-their-small-arms-arsenal/72006282/ |title=Marines unveil plan to modernize their small arms arsenal |first= James K. |last=Sanborn |date=17 September 2015 |newspaper=Marine Corps Times |url-status=live |archive-url=https://web.archive.org/web/20160105102710/http://www.marinecorpstimes.com/story/military/tech/2015/09/17/marines-unveil-plan-modernize-their-small-arms-arsenal/72006282/ |archive-date=2016-01-05}}</ref> The first phase of conversions was completed in March 2017, with 3,600 M2A1s planned to be fielded by the Marines in total.<ref>{{cite news |url=https://www.marinecorpstimes.com/articles/improved-50-caliber-machine-gun-hits-fleet |title=Improved .50-caliber machine gun hits fleet |first=Todd |last=South |date=27 April 2017 |newspaper=Marine Corps Times |url-status=live |archive-url=https://web.archive.org/web/20170428002038/https://www.marinecorpstimes.com/articles/improved-50-caliber-machine-gun-hits-fleet |archive-date=2017-04-28}}</ref> The [[Israel Defense Forces]] adopted the M2-HQCB (the commercial version of the M2A1) in 2012 as a replacement to the M2HB.<ref>{{cite web |url=http://www.idf.il/1133-14686-he/Dover.aspx |title=הכירו את כלי הנשק החדשים של זרוע היבשה |trans-title=Familiarize yourself with the new weapons of the land arm |date=2012 |website=[[Israel Defense Forces]] |language=he |url-status=dead |archive-url=https://web.archive.org/web/20160911000141/http://www.idf.il/1133-14686-he/Dover.aspx |archive-date=11 September 2016}}</ref>