The Primary Weapons Systems MK111 MOD 1-M Upper Receiver, 338 ARC, 11.85" Long-Stroke Gas Piston, Black is a compact, hard-running upper built around PWS’s proven long-stroke gas piston system. Its Boise-made 11.85 inch barrel with a 1:8 twist is paired with a PWS FRC 1-port compensator to help control recoil and muzzle movement, while the free-float PicLok handguard offers generous M-LOK slots and a full-length top rail for optics and accessories.
This assembled upper is ideal for shooters who want a reliable upgrade for their AR platform in 338 ARC, whether for range work, training, or hunting where the cartridge’s ballistics can shine. Suppressor optimization and the adjustable three-setting gas block help keep the system cleaner with reduced gas blowback, and the included Radian Raptor ambidextrous charging handle supports smooth operation for right- and left-handed users. The design reflects Primary Weapons Systems’ focus on durability, thoughtful engineering, and consistent accuracy.
- Manufacturer: Primary Weapons Systems
- Model: MK111 MOD 1-M Upper, 338 ARC
- Caliber: 338 ARC
- Action: Semi-Auto
- Operating System: Long-Stroke Gas Piston
- Gas Block: 3-Setting, Adjustable
- Gas System Length: Carbine
| __Material | 7075-T651 Aluminum, Steel |
| __Firearm Type | Rifle, SBR, Tactical Pistol |
| __Caliber | UNKNOWN |
| __Capacity | NA |
| __Barrel Length | NA |
| __Optic Footprint | NA |
| __Action | NA |
| __Model | MK111 MOD 1-M Upper |
