Rheinmetall’s HAMMR Brings Semi-Auto 40mm Firepower to Army Competition
American Rheinmetall Munitions has submitted its HAMMR, a shoulder-fired, semi-automatic 40mm grenade launcher, for the U.S. Army’s Precision Grenadier System competition.
For anyone familiar with Warhammer 40,000, HAMMR looks like the defense industry’s latest attempt to build a real-world bolter. It is not firing rocket-propelled “bolts,” but the comparison is hard to miss: an oversized, rifle-shaped weapon feeding explosive projectiles from a detachable magazine and delivering them as fast as the shooter can pull the trigger.
The Highly-Advanced Multi-Mission Rifle, better known as HAMMR, combines a magazine-fed launcher, programmable 40mm ammunition and computerized fire control. Its mission is to give one soldier the ability to rapidly hammer enemies behind cover, strike targets beyond conventional grenade-launcher distances and deliver different effects without waiting for mortars or other supporting weapons.
HAMMR Builds on Rheinmetall’s SSW40
The American prototype is based on Rheinmetall’s SSW40, a shoulder-fired, self-loading grenade launcher developed around 40mm medium-velocity ammunition. The baseline SSW40 weighs approximately 8.8 pounds empty and measures about 31.5 inches long—roughly the dimensions of a compact battle rifle, although considerably heavier once equipped with its sight, magazine and ammunition. It uses a self-regulating hydropneumatic recoil system intended to make the powerful medium-velocity cartridges controllable from the shoulder.
Rheinmetall publicly demonstrated the launcher in 2025, firing at steel targets from 100 to 500 meters. Test shooters reportedly found its recoil comparable to conventional 40mm low-velocity launchers despite the more powerful ammunition. The company claims an engagement range of up to 900 meters with appropriate medium-velocity projectiles.
That does not necessarily mean an Army grenadier will reliably hit point targets at 900 meters. Final effective range, hit probability and ammunition performance must be established through Army testing. It nevertheless represents a major increase over the familiar single-shot M320.
Programmable Grenades Defeat Enemies Behind Cover
HAMMR’s real advantage is not simply its range. It is the marriage of ammunition and fire control. The weapon is paired with an Aimpoint FCS15 sight that incorporates ranging and ballistic-computation capabilities. The operator ranges the target, the sight calculates the firing solution, and compatible ammunition is programmed to detonate at the chosen distance.
An enemy hiding behind a wall, inside a trench or below a rooftop parapet is no longer protected simply because the grenadier cannot land a conventional impact round directly beside him. A programmed grenade can burst above or just beyond the obstacle.
Rheinmetall says its 40mm medium-velocity family includes high-explosive fragmentation, programmable airburst, multi-mission, high-explosive dual-purpose and training ammunition. The company claims its HEDP projectile can penetrate four inches of rolled homogeneous armor, potentially giving HAMMR utility against light vehicles and fortified positions.
The system also retains compatibility with qualified 40mm low-velocity ammunition already in the Army inventory. That is an important logistical advantage over completely new calibers.
Can HAMMR Avoid the XM25’s Fate?
The concept inevitably recalls the XM25, the Army’s 25mm airburst weapon. The XM25 underwent combat evaluation in Afghanistan but was ultimately canceled after years of problems involving weight, reliability, cost and program management. The Army formally terminated the program in July 2018.
HAMMR approaches the mission with a substantially larger 40mm projectile, an existing launcher design and compatibility with conventional ammunition. Its magazine-fed action also allows rapid correction shots and engagement of multiple targets without manually loading another grenade after every trigger pull.
The tradeoff is ammunition weight. Five 40mm grenades are not light, and a grenadier must carry the launcher, electronic sight, loaded magazines and a useful combat supply. Cost, battery life, fuze reliability and performance against moving drones also remain unanswered questions.
Still, HAMMR is one of the most interesting infantry weapons currently competing for an Army contract. If Rheinmetall can deliver the advertised range, reliability and controllability, it could give an American rifle squad organic firepower once reserved for heavier support weapons.
It is not a rifle in the traditional sense. It is a shoulder-fired, semi-automatic 40mm problem solver—and the Army is now deciding whether HAMMR is the tool its grenadiers have been waiting for.
About Duncan Johnson:
Duncan Johnson is a lifelong firearms enthusiast and unwavering defender of the Second Amendment—where “shall not be infringed” means exactly what it says. A graduate of George Mason University, he enjoys competing in local USPSA and multi-gun competitions whenever he’s not covering the latest in gun rights and firearm policy. Duncan is a regular contributor and editor-in-chief for AmmoLand News and is responsible for AmmoLand’s daily gun-rights reporting and industry coverage.