Heckler & Koch MR223 A3

The self-loading repeater MR 223 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.

On the upper, a STANAG-4694 profile without cant is installed. It is noteworthy that the magazine release lever and bolt catch lever are present on both sides. The system is rounded off by a protective wall against unintentional discharge when laying down the weapon with an open bolt. The 90° safety lever is also installed on both sides and operates a ambidextrous safety with a new control surface, and an additional spring in the trigger mechanism ensures this feature. If the safety is engaged in a relaxed state, the special geometry ensures that the two arms of the safety spring are bent apart. When the hammer is cocked, the springs quickly return to their original position, resting under the safety surface and thus blocking the trigger. The simple design of the trigger safety ensures absolute reliability and longevity.

Gas operation
Like the vast majority of all modern self-loaders in centerfire configuration, the H&K MR 223 A3 operates as a gas-operated loader with a rotating bolt. Unlike a classic AR-15 design, the propellant gases tapped off in 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 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 contamination 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 reduces the usual dirt deposits to a minimum.

The barrel
Heckler and Koch offers barrel lengths of 11 inches (27.9 cm), 14.5 inches (36.8 cm), or 16.5 inches (41.9 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 rounded off 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 escaping from 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 is equipped with 7 radial locking lugs and is significantly more robust than that of the AR15.

It is noteworthy that there is 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 to a block on the barrel extension - the latter serves to prevent the use of military bolt carrier groups on the MR223.

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 equipped with several waterproof compartments that can be used for storing batteries and some small spare parts.
The Slim-Line handguard is equipped with HKey interfaces and is rounded off by a STANAG-4694 profile at 12 o'clock and a MIL-STD-1913 Picatinny profile at 6 o'clock.