The US Army is moving to supplement and superseded the M993 Armour Piercing round and M80A1 Enhanced Performance Round, introduced back in 2016, with the new 7.62x51mm XM1158 Advanced Armor Piercing Round. In October 2019, the Army authorised the urgent materiel release of the XM1158 round to accelerate its fielding. The Army is planning on a full materiel release for the round in FY 2020.

The XM1158 round was rumoured to have been the partner ammunition to the US Army’s ill-fated Interim Combat Service Rifle (ICSR). The 2019 Annual Report from the Director, Operational Test and Evaluation (DOT&E) confirms that the “XM1158 utilizes a core and penetrator encapsulated in a reverse-drawn copper jacket.”

According to the FY 2019 annual report from the Office of the Director, Operational Test and Evaluation, the “DOT&E will report on XM1158 performance in a classified lethality report upon live fire test completion to support full materiel release in FY20.” So it will likely be a while before we know the round’s true capabilities.

The M240 is one of the Army’s weapon systems which will be using the new XM1158 round (U.S. Army photo by Sgt. Leron G. Richards)

XM1158 was approved for development in 2015 and the Army completed initial live fire testing of the XM1158 in March 2019 to support urgent materiel release. The testing was “conducted in accordance with the DOT&E-approved live fire strategy.” According to the DOT&E’s December 2019 report:

The Army used barrier-protected gelatin targets to enable credible computer modeling of XM1158 performance with the Operational Requirements-based Casualty assessment/Static Dynamic Framework model (ORCA/SDF). To support full materiel release, the Army plans additional testing against other light material barriers and targets to determine the projectile’s ability to perforate operationally relevant targets. The Army will accredit ORCA/SDF to support full materiel release.

The new 7.62x51mm Advanced Armor Piercing Round will replace the current M993 AP round in the M993-linked configuration to provide improve lethality compared to the current M80A1 and M993 cartridges. The round can be used in the Army’s  M240 series of machine guns; the Mk 48 machine gun; and the M110 series, Mk 17, Mk 14, and M14 series rifles.

Source