Preview – PWS MK109 300Blk

Photography by Straight 8

Primary Weapon
PWS’ MK109 Combines the Advantages of an SBR with the Proven Terminal Ballistics of the .300 Blackout Round

Until recently, AR pistols were rightly regarded as the Miley Cyrus of the firearms world — temperamental, attention-seeking, and stridently obnoxious. And like their pop tart counterpart, while no doubt good for a few minutes worth of fun, they were largely useless for any serious work.

In the last couple of years, two developments have come along to change this state of affairs. The first is the refinement of the .300 Blackout cartridge, developed specifically for use in short barrels. Unlike 5.56mm NATO, which in a 9-inch tube launches most of its powder charge unburned into the atmosphere, the .300 BLK achieves complete combustion thanks to its use of pistol propellant to drive a wide range of .30-caliber projectiles. The second innovation has been the introduction of SIG SAUER’s SB15 “arm brace,” which has made AR pistols much easier to shoot.

If we combine the two ingredients, we get a dish that looks like a pretty versatile short-range firearm — one that offers effective terminal ballistics in a handy, ergonomic package. While it’s never going to win a three-gun competition or make the top 10 at Camp Perry, the result is well suited to home defense or taking medium-sized game when loaded appropriately.

The Long and Short of it
Primary Weapons Systems (PWS) has made a name for itself by bringing innovative approaches to the piston AR market, in particular by bucking the trend toward short-stroke piston systems. Instead, the piston and op rod are attached to the bolt carrier in much the same way as an AK platform. While this long-stroke system usually results in a touch more felt recoil due to increased reciprocating mass, there are benefits to be had in terms of fewer parts to fail.

Looking the gun over from stem to stern, the muzzle is tipped with a PWS Triad muzzle brake, which acts as both flash hider and compensator. It attaches to the barrel by means of 5⁄8×24 threads, the shoulder of which clears the rail system by a ¼ inch, allowing a suppressor to be screwed directly to the barrel. Or the end user can choose to install any one of a number of quick-attach devices.

PWS’s slim, KeyMod handguard arrives from the factory with a pair of 2-inch-long rail sections mounted at the 3 and 9 o’clock positions. So, in keeping with its potential role as a home-defense weapon, we mounted up a SureFire Scout Light and pressure pad, using Manta rail covers to keep everything in place. It looks like 2014 promises to be the year of the KeyMod, but until accessory manufacturers catch up, users are forced to rely on the tried-and-true 1913 Picatinny rail to bolt gadgets to their guns.

The handguard itself measures 1.75 inches across the flats and 2.125 inches from base to top of Pic rail and is attached to the upper receiver by means of a proprietary barrel nut and six Allen head screws at the 3, 6 and 9 o’clock positions. Removing it reveals a non-adjustable gas block, secured via a threaded barrel section mated to a knurled nut. The gas tube vents on its underside, just in front of the barrel nut, meaning that unlike an AK, the system is pressurized for almost the entire stroke. This, coupled with the gas port location a full 4.5 inches from the muzzle, should mean that dwell time is not an issue and that, should it be necessary, the gun can be fine tuned by changing buffer weights and recoil spring length.

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