Primary Weapons Systems Compound, Semi-automatic Rifle, AR-15, 223 Wylde, 16.1 Barrel, 1:8 Twist, FSC556 Muzzle Device, MLOK Handguard, Anodized Finish, Black, Magpul Stock, Magpul Grip, 1 Magazine, 30 Rounds MK1-CPP-223-16 Primary Weapons Systems was formed by firearm enthusiasts in 2008. Starting out by producing muzzle devices, they tested their compensators on all different types of rifles - from M4s to AK-47s. After using both styles of rifles in testing with high round counts, the difference in maintenance needed was both astounding. From that basic realization, the PWS long-stroke piston system was born; keeping the core values of the AR-15 design, while also lessening the need for maintenance in high-volume fire situations and adverse conditions. The Compound Rifle is a combination of a Mod 1 upper, with the Mk1 Mod 2 Lower.