Editing MBT-70 (section)

==XM803==
[[File:XM803 U.S. Army Armor & Cavalry Collection.jpg|thumb|XM803 at the [[U.S. Army Armor & Cavalry Collection]]. Note the two return rollers, versus three on the MBT-70.]]
Work began on converting the existing MBT-70 design into a low-cost "austere" alternative that would use only American-made components, resulting in the visually similar XM803 prototype. Congress hoped to drive down the per-unit cost to $500,000–$600,000, saving $200,000 per tank versus the MBT-70.<ref name="Bonn and Washington split"/>

The largest cost savings came from a switch to a less expensive steel armor plating. An American-made engine also reduced costs. The design was slightly heavier and slower.<ref name="slower, heavier">{{cite news |last1=Prina |first1=L. Edgar |title=New 'Austere' Army Tank Nearly Ready |url=https://www.newspapers.com/image/735262527/?terms=xm803&match=1 |access-date=12 November 2021 |work=The News Tribune |date=4 August 1970}}</ref> General Motors received a $16.5 million contract to develop the tank in July 1971.<ref>{{cite news |title=Michigan Business in Brief |url=https://www.newspapers.com/image/99029191/?terms=xm803&match=1 |access-date=12 November 2021 |work=The Detroit Free Press |date=30 July 1971}}</ref> Systems were simplified or eliminated altogether to save costs.{{sfn|Kelly|1989|pp=40}} The XM150E5 gun-launcher was replaced with an XM150E6, which included a closed breech scavenging system.{{sfn|Hunnicutt|2015|p=151}} A 24-round General Motors autoloader was installed. Ammunition capacity was increased to 50 rounds.{{sfn|Hunnicutt|2015|p=152}} The commander's 20&nbsp;mm cannon was replaced by a [[.50 caliber]] [[M85 machine gun]].{{sfn|Hunnicutt|2015|p=183}} The driver's escape hatch was deleted and his television, as well as those of all the other crew, were eliminated.{{sfn|Hunnicutt|2015|p=147}} The Continental AVCR-1100-3B engine was derated to {{convert|1250|hp}} at 2600 rpm and paired to a General
Motors XHM-1500-2B transmission.{{sfn|Hunnicutt|2015|p=154-155}} A simplified National Water Lift hydropneumatic suspension was installed. Side skirts were installed, which allowed some armor to be removed from the hull.{{sfn|Hunnicutt|2015|p=156}} Meanwhile, the U.S. Army studied installing a [[gas-turbine]] [[Avco-Lycoming AGT1500|AGT-1500]] generating {{convert|1500|hp}} (this was the engine that would come to power the [[M1 Abrams]]).{{sfn|Hunnicutt|2015|p=154}}

Only one of the two pilot vehicles authorized for construction was completed.{{sfn|Hunnicutt|2015|p=158}} In addition, a surrogate vehicle based on the components of MBT-70 {{failed verification span|text= pilot #4,|date=June 2024}} the M60 and the [[M88 armored recovery vehicle]], was constructed.<ref>{{cite AV media | people = Sofilein | date = 5 January 2020 | title = Meet the 'Pigg'! MBT70/XM803 Hybrid tank at NACM Ft Benning | type =video | url =https://www.youtube.com/watch?v=DElj7GfwtlI | access-date =27 June 2024}}
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These changes were ultimately insufficient to allay concerns about the tank's cost.{{sfn|Hunnicutt|2015|p=158}} In September 1971, an amendment by Senator [[Thomas Eagleton]] was defeated that would cut $35.3 million in funding for XM803 prototype production.<ref>{{cite news |title=Pullout Deadline Voted by Senate |url=https://www.nytimes.com/1971/10/01/archives/pullout-deadline-voted-by-senate-2d-such-plan-by-mansfield-is.html |access-date=12 November 2021 |work=The New York Times |date=1 October 1971}}</ref><ref>{{cite news |title=U.S. Withdrawal Deadline Again Approved by Senate |url=https://www.newspapers.com/image/68803844/?terms=%22xm803%22&match=1 |access-date=12 November 2021 |work=Kingsport News |agency=UPI |date=1 October 1971}}</ref> but in December 1971, Congress canceled the tank in the defense appropriation bill.<ref name="xm803 terminated">{{cite news |title=U.S. Germany Abandon 'Dream Tank' |url=https://www.newspapers.com/image/7447436/?terms=xm803&match=1 |access-date=12 November 2021 |work=Lubbock Avalanche-Journal |agency=UPI |date=16 December 1971}}</ref> The bill appropriated $20 million for cancelation costs and $20 million for the development of a new tank program.<ref>{{cite news |last1=Turner |first1=Bob |title=Congress Kills Tank Program |url=https://www.newspapers.com/image/332215721/?terms=xm803&match=1 |access-date=12 November 2021 |work=The Tampa Tribune |date=20 December 1971}}</ref> This became the XM1 design project, which led to the production-model [[M1 Abrams]] tank.