Editing M1 Abrams (section)

===Starting over===
The Army began the '''XM815''' project in January 1972. The Main Battle Tank Task Force (MBTTF) was established under Major General [[William Robertson Desobry|William Desobry]]. The task force prepared design studies with the technical support of [[Tank-automotive and Armaments Command]] (TACOM).{{sfn|Hunnicutt|2015|p=161}} TACOM began examining specific goals. To this end, a new design basis emerged in February 1973. It had to defeat any hit from a Soviet gun within {{convert|800|m|abbr=on}} and 30 degrees to either side. The tank would be armed with the 105&nbsp;mm [[M68 (tank gun)|M68 gun]], a licensed version of the [[Royal Ordnance L7]], and a 20&nbsp;mm version of the [[M242 Bushmaster]].{{sfn|Hunnicutt|2015|p=202}} The Army later deleted the latter from the design, seeing it as superfluous.{{sfn|Hunnicutt|2015|p=178}}

In spring 1972, Desobry was briefed by the British on their own newly developed [[Chobham armour|"Burlington" armor]] from the [[British Army]]'s labs. The armor performed exceptionally against [[shaped charge]]s such as HEAT rounds. In September, Desobry convinced the Army to incorporate the new armor. To take full advantage of Burlington, also known as Chobham, the new tank would have to have armor around two feet thick (for comparison, the armor on the M60 is around four inches thick). General [[Creighton Abrams]] set the weight of the new tank at {{convert|53|t}}. The original goal of keeping weight under {{convert|45|t}} was abandoned.{{sfn|Kelly|1989|pp=111–130}}

At the time, the Pentagon's procurement system was beset with problems being caused by the desire to have the best possible design. This often resulted in programs being canceled due to cost overruns, leaving the forces with outdated systems, as was the case with the MBT-70. There was a strong movement within the Army to get a new design within budget to prevent the MBT-70 experience from repeating itself. For the new design, the Army set the design-to-unit cost at no more than $507,790 ({{inflation|US|507,790|1972|fmt=eq|r=-3}}).<ref name=bail>{{cite news |newspaper= Washington Monthly |date=1987 |url= https://www.thefreelibrary.com/The+first+Chrysler+bail-out%3b+the+M-1+tank.-a04696991 |title=The First Chrysler Bail-Out: The M-1 Tank |access-date=12 November 2019 |archive-date=12 November 2019 |archive-url=https://web.archive.org/web/20191112144938/https://www.thefreelibrary.com/The%2Bfirst%2BChrysler%2Bbail-out;%2Bthe%2BM-1%2Btank.-a04696991 |url-status=live}}</ref>

The Pentagon's approach to control of research and development was modified with the XM1. Previous acquisition strategy called for a significant amount of the design work to be done by the government. Under the new framework, contractors would competitively bid their own designs rather than compete solely for the right to manufacture the end product.{{sfn|Kelly|1989|p=13–43}}

In January 1973, the U.S. Army issued the '''XM1''' (as the XM815 had been renamed in November 1972) [[request for proposal]]s.{{sfn|Information Spectrum|1983|p=B-2, B-3}} In May 1973, [[Chrysler Defense]] and [[General Motors]] submitted proposals. Both were armed with the 105&nbsp;mm M68 gun, the licensed L7, and the 20&nbsp;mm Bushmaster. Chrysler chose a 1,500&nbsp;hp Lycoming AGT1500 [[gas turbine]] engine. GM's model was powered by a 1,500&nbsp;hp diesel engine similar to that used on the American MBT-70 and XM803.{{sfn|Hunnicutt|2015|p=176}}