Primary Weapons Systems MK1 Mod 1-M Upper Features The Primary Weapons Systems MK1 Mod 1-M Upper runs the company s long-stroke piston system which keeps combustion gases out of the receiver for cleaner more reliable cycling compared to a direct-impingement setup. Chambered in .223 Wylde the 11.85 inch black anodized barrel is short enough for maneuverability in close quarters while remaining accurate with both .223 Rem and 5.56 NATO ammunition. Forward assist controls give the shooter a way to fully seat the bolt in the rare event it hangs up adding a layer of reliability that some AR builds omit. The fully forged receiver provides the strength to handle sustained hard use in demanding environments. A free-float M-LOK handguard lets the shooter mount accessories directly to the rail system without touching the barrel keeping point of impact consistent as the rifle heats up or gear is added and removed. This upper is built for direct drop-in compatibility with standard AR-15 lowers so no special fitting is required to complete the rifle. The black anodized finish matches typical AR furniture while resisting wear from repeated handling and field use. For AR-15 owners who have grown to trust the PWS piston system this MK1 Mod 1-M Upper is a straightforward upgrade path to more reliable cleaner-running operation. Primary Weapons Systems MK1 Mod 1-M Upper Specifications Manufacturer: Primary Weapons Systems Model: MK1 Mod 1-M Upper Caliber: .223 Wylde Barrel Length: 11.85 Barrel Finish: Black Anodized Compatible Hosts: AR-15 Handguard: M-LOK Free Float Available At: GrabAGun