Heckler & Koch MR308 A3

The self-loading repeater MR308 A3 from Heckler & Koch creates the incredible symbiosis of reliable German military technology and the simple, yet proven design of the AR 15 systems.
The advanced version A3 impresses sports shooters and hunters with its ambidextrous operation. The system is complemented by the NATO-STANAG-4179 (Draft) magazine well, the Slim Line handguard, the included quick-change magazine, and the length-adjustable Slim Line stock.

The housing and stock The receivers are made from a high-strength aluminum-zinc alloy, which is comparable in properties to most steels. These material properties have achieved excellent results in all conducted hardness and extreme tests. The upper features a STANAG-4694 profile without cant. Notably, the magazine release lever and bolt catch lever are present on both sides. The system is rounded off with a protective wall against unintentional discharge when placing the weapon down with an open bolt. The 90° safety lever is also installed on both sides and operates a dual-sided safety with a new control surface, and an additional spring in the trigger mechanism ensures this feature. If the safety is engaged in the relaxed state, the special geometry ensures that the two arms of the safety spring are bent apart. When the hammer is cocked, the springs snap back into their original position, resting under the safety surface and thus blocking the trigger. The simple construction of the trigger safety guarantees absolute reliability and longevity.

Gas operation Like the vast majority of all modern self-loaders in centerfire configuration, the H&K MR308 A3 operates as a gas-operated loader with a rotating bolt. Unlike a classic AR-15 design, the propellant gases tapped from the barrel do not flow directly onto the bolt carrier through a tube, but onto a short-stroke gas piston. In an indirect short-stroke gas piston system, the gas piston housed in the gas block moves separately from the bolt. It imparts a short mechanical impulse to a connecting rod that drives the bolt. This rod then remains stationary, as the kinetic energy is sufficient to initiate the cycling process. The gas-operated loader from Heckler & Koch shines with excellent long-term functionality, as heat and fouling are significantly reduced by the short-stroke gas piston system. The self-loader is characterized by outstanding operational reliability. The gas system was developed for military purposes and has proven itself in military technology over the years. The drive system minimizes typical dirt deposits to a minimum.

The barrel Heckler and Koch offers barrel lengths of 13 inches (33 cm), 16.5 inches (41.9 cm), or 20 inches (50.8 cm) for the self-loading repeater. These are made from cold-hammered forged steel and feature right-hand twist rifling with 6 right-hand grooves at a ratio of 1:7. The manufacturing process requires special high-quality steel grades and a chrome lining of the bore to achieve a barrel that still exhibits high precision even after more than 20,000 shots. The barrel is finished with its muzzle thread in M15x1.

The bolt The bolt carrier group is not equipped with a gas key, i.e., a small tube through which the gas exiting the barrel is directed - as required by the direct gas impact system - but with a monolithic prism onto which the weapon's rod transmits the kinetic impulse. The chrome-plated bolt features 7 radial locking lugs and is significantly more robust than that of the AR15.

Noteworthy is the presence of a contrast spring on the firing pin to avoid marking the primer and a possible "slam fire" - a typical problem of the AR15 - as well as an automatic safety for the firing pin, which is deactivated by the hammer in the firing position. The main recoil spring in the buffer tube is 20 percent stronger than the original spring and uses a newly developed buffer. The end of the bolt carrier group has also been partially redesigned, as it now features a large sliding surface. The bolt carrier group has a cutout on the left side that corresponds with a block on the barrel extension - the latter serves to prevent the use of military bolt carrier groups on the M308 A3.

The stock The length-adjustable Slim-Line stock can be fixed in 6 different detent positions and is equipped with several waterproof compartments that can be used for storing batteries and some small spare parts. The folding stock is also equipped with several waterproof compartments for storing batteries and small spare parts. The Slim-Line handguard features HKey interfaces and is complemented by a STANAG-4694 profile at 12 o'clock and a MIL-STD-1913 Picatinny profile at 6 o'clock.

Caliber: .308Win

Technical data

Type of weapon: Self-loading rifle
Trigger: Pressure point trigger
System: Indirect gas-operated loader
Safety: 2-position safety
Barrel length:
13 inches – 33 cm
16.5 inches – 41.9 cm
20 inches – 50.8 cm
Muzzle thread: M15x1
Sights: Folding front sight with quick-change sight
Magazine capacity: 10 rounds
Stock material: Plastic
Stock shape: Six-position length-adjustable Slim-Line stock
Handguard: Slim-Line handguard with HKEY interfaces, STANAG-4694 profile, and MIL-STD-1913 profile
System housing: Forged aluminum-zinc alloy
Total length: 71.1 cm – 107.2 cm
Weight: 4.5 kg