In April 2016 Heckler & Koch confirmed that a lighter version of the G28 had won the United States Army's Compact Semi-Automatic Sniper System contract to replace the M110 Semi-Automatic Sniper System.
It is designated as the M110A1 and uses an aluminum upper receiver instead of steel to meet weight requirements, weighing 8.4 lb (3.8 kg) unloaded and reaching some 15 lb (6.8 kg) loaded and with accessories; the M110A1 features a Geissele M-LOK rail handguard, Schmidt & Bender 3–20×50 PM II Ultra Short telescopic sight, Geissele optic mount, OSS SRM6 suppressor, 6-9 Harris bipod and mount, and a collapsible stock with adjustable comb.
In May 2018, the U.S. Marine Corps will begin receiving the CSASS, also to replace the M110.

In March 2018, the Army announced that a version of the G28/M110A1 would be issued to infantry squads as the service's standard Squad Designated Marksman Rifle (SDMR).
Issuing a 7.62×51mm NATO SDMR is meant to increase individual squads' ability to defeat enemy body armor that standard 5.56×45mm NATO rounds cannot penetrate.
The M110A1-based rifle will replace the M14 EBR, in use by the Army since 2009, but because it was based on an operational needs statement it had to be turned in by units at the end of a combat deployment.
Unlike the sniper configuration, the SDMR model will be equipped with a different buttstock and barrel twist than the CSASS model.
The marksman version is fitted with a simpler SIG TANGO6 1-6×24 telescopic sight to make quick adjustments between 0–600 m (0–656 yd), and it fires M80A1 Enhanced Performance Rounds or XM1158 Advanced Armor Piercing Rounds rather than sniper rounds; it will be fielded with a suppressor to make the marksman less identifiable with louder 7.62×51mm NATO rounds.
The SDMR TANGO6 1-6×24 telescopic sight features a red horseshoedot for fast aiming and an illuminated Extended Range Bullet Drop Compensation (BDC) illuminated front focal plane reticle.
Roughly 6,000 are planned to be fielded with one per squad in infantry, engineer and scout formations.
U.S. Army combat units began receiving the first M110A1 SDMRs in April 2020.
In April 2016 Heckler & Koch confirmed that a lighter version of the G28 had won the United States Army's Compact Semi-Automatic Sniper System contract to replace the M110 Semi-Automatic Sniper System. It is designated as the M110A1 and uses an aluminum upper receiver instead of steel to meet weight requirements, weighing 8.4 lb (3.8 kg) unloaded and reaching some 15 lb (6.8 kg) loaded and with accessories; the M110A1 features a Geissele M-LOK rail handguard, Schmidt & Bender 3–20×50 PM II Ultra Short telescopic sight, Geissele optic mount, OSS SRM6 suppressor, 6-9 Harris bipod and mount, and a collapsible stock with adjustable comb. In May 2018, the U.S. Marine Corps will begin receiving the CSASS, also to replace the M110.
In March 2018, the Army announced that a version of the G28/M110A1 would be issued to infantry squads as the service's standard Squad Designated Marksman Rifle (SDMR). Issuing a 7.62×51mm NATO SDMR is meant to increase individual squads' ability to defeat enemy body armor that standard 5.56×45mm NATO rounds cannot penetrate. The M110A1-based rifle will replace the M14 EBR, in use by the Army since 2009, but because it was based on an operational needs statement it had to be turned in by units at the end of a combat deployment. Unlike the sniper configuration, the SDMR model will be equipped with a different buttstock and barrel twist than the CSASS model. The marksman version is fitted with a simpler SIG TANGO6 1-6×24 telescopic sight to make quick adjustments between 0–600 m (0–656 yd), and it fires M80A1 Enhanced Performance Rounds or XM1158 Advanced Armor Piercing Rounds rather than sniper rounds; it will be fielded with a suppressor to make the marksman less identifiable with louder 7.62×51mm NATO rounds. The SDMR TANGO6 1-6×24 telescopic sight features a red horseshoedot for fast aiming and an illuminated Extended Range Bullet Drop Compensation (BDC) illuminated front focal plane reticle. Roughly 6,000 are planned to be fielded with one per squad in infantry, engineer and scout formations. U.S. Army combat units began receiving the first M110A1 SDMRs in April 2020.
Heckler & Koch HK417