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Primary Weapons Systems MK111 Piston Upper (11.85" .223 Wylde Barrel)

  • Primary Weapons Systems MK111 Piston Uppers
  • Primary Weapons Systems MK111 Mod 2 Piston Upper
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  • Primary Weapons Systems Piston Bolt Carrier Group
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  • Primary Weapons Systems Piston System
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Primary Weapons Systems MK111 Piston Upper (11.85" .223 Wylde Barrel)

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$1,349.95 $999.95

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MPN: M111UA0B / 2M111UA0B


  • PWS carbine-length long-stroke piston system - combines the agility of the AR-15 with the reliability of the AK-47 into a sleek and efficient design
  • 3 easy to adjust gas settings 
  • Continuous Picatinny top rail
  • Free Float KeyMod system w/ PicMod Technology in MOD 2 models - The new technology allows you to mount KeyMod attachments anywhere on your handguard and mount Picatinny accessories directly to the recessed Picatinny rail section at the end of the handguard
  • Light-weight forged upper in MOD 2 models - No forward assist and material removed from less structurally important location for weight reduction
  • Increased carrier mass to extend dwell time and delay unlock
  • Lithium Embedded Salt Nitro-Carburized (FNC LIFE HD) coated barrel and bolt carrier for durability, corrosion resistance and to reduce friction


  • Caliber: .223 Wylde
  • Finish: Type III Class 2 Hardcoat Anodized Finish
  • Upper Receiver:
    • MK1 MOD 1-P: Forged Flat Top Upper - Made from 7075-T6 aluminum
    • MK1 MOD 2: Forged Lightweight Flat Top Upper (No forward assist) - Made from 7075-T6 aluminum 
  • Handguard:
    • MK1 MOD 1-P: 10-inch KeyMod Rail System - Made from 6061-T6 aluminum
    • MK1 MOD 2: 11-inch KeyMod Rail System with PicMod Technology - Made from 6061-T6 aluminum
  • M4 Feed Ramps: Yes
  • Muzzle Device: PWS Triad 556 flash suppressor
  • Barrel: 11.85” 1:8 Twist Modify Low-Stress profile .223 Wylde 416R Stainless Steel Barrel (Black finish)
  • Muzzle Thread Pattern: 1/2"-28
  • Gas Block: PWS Long Stroke Piston System - 3-Position Adjustable Gas Block
  • Gas Length: Carbine-Length
  • Bolt Carrier Group: PWS Long Stroke Piston Bolt Carrier Group
  • Charging Handle: Bravo Company Mod4 Extended Charging Handle
  • Weight: 
    • MK1 MOD 1-P: 4 lbs.
    • MK1 MOD 2: 3 lbs. 12.8 oz.
  • Overall Length: 20.6"


  • 3x RailSacles covers
  • 1x PWS gas adjustment tool

 *This upper receiver assembly has a barrel that is shorter than 16". This upper is only for use on AR pistol lower receivers and NFA registered Short-Barreled Rifle (SBR) lower receivers. All NFA laws apply!




Those operators who rely heavily on the use of suppressors have long been wary of changes to the standard rifle system they have long depended on. Today, Primary Weapons Systems offers a long piston AR upper to work with their weapon systems. The PWS MK111 is a fully assembled long piston operated upper with an 11.85 inch .223 Wylde Barrel that was designed especially for use with the shortest working suppressed rifle systems. The MK111 had been successfully battle tested in a number of arenas and has proven lethal at up to 300 meters.

The MK111 is built on the Primary Weapons Systems MK1 upper, an efficient long stroke piston design that uses a single-unit operation system that joins the bolt carrier group and floating piston head with a long operating rod. The result is a system with fewer individual moving parts. This system is less finicky than direct impingement AR systems and more flexible than the stolid AK-47. The PWS MK111 lets you operate with less risk of failure and a far easier maintenance routine than traditional AR systems. The operator can use the multi-selection adjustable gas block to customize gas tuning allow optimization for multiple ammunition and accessory combinations.

Whether you choose the MK111 in a PWS Mod 1 or a PWS Mod 2 you’ll receive the same awesome trouble-free PWS MK1 performance and extraordinary service life from components treated with a lithium embedded salt nitro-carburized processed. This FNC LIFE HD treatment alters the make-up of the outer layer of steel, creating a nearly indestructible surface. This finish doesn’t wear, crack or flake off like chrome coatings, and doesn’t alter the dimensions of the rifles working components.

The MK1 Upper is available in two distinct versions, Mod 1 and Mod 2. While both versions are outstanding long piston AR uppers, they may appeal to different types of operators. The PWS Mod 1 Upper in more consistent with what die-hard traditional AR fans expect, including a forward assist and a heavier receiver as a whole. The PWS Mod 2 features a sleeker receiver, which leaves off the forward assist and trims off a little extra weight through careful machining of the forged upper. The result is a lighter-weight upper that still maintains the unmatched strength of a quality forged upper while giving the billet devotees a run for their money in both reduced mass and streamlined appearance.

The new Primary Weapons Systems upper retains the adjustable gas block from the previous version but it simplifies operation by cutting back the adjustment options to three positions that will do it all in the field. Simply choose the position you need for unsuppressed ammunition, for low power suppressed ammunition or the third for mid to high powered ammunition under suppression.

Whether you chose the PWS MK1 Mod 1 Upper or the Mod 2 you’ll be a rung up the evolutionary ladder. Because It’s Time, Primary Weapons Systems MK111.

PWS MK1 Series Rifle System Overview 05:41
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