MPN: M114UA0B / 2M114UA0B


  • Pinned and welded PWS FSC (Flash Suppressing Compensator) to maintain legal 16" barrel rifle requirements
  • 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 M-LOK system w/ PicMod Technology in MOD 2 models - The new technology allows you to mount M-LOK 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: 5.56 NATO / .223 Rem.
  • Chamber: .223 Wylde
  • Finish: Type III Class 2 Hardcoat Anodized Finish
  • Upper Receiver:
    • MK1 MOD 1-M: Forged Flat Top Upper - Made from 7075-T6 Aluminum
    • MK1 MOD 2-M: Forged Lightweight Flat Top Upper (No forward assist) - Made from 7075-T6 Aluminum
  • Handguard:
    • MK1 MOD 1-M: 13.6-inch M-LOK Rail System - Made From 6061-T6 Aluminum
    • MK1 MOD 2-M: 13.6-inch M-LOK Rail System with PicMod Technology - Made From 6061-T6 Aluminum
  • M4 Feed Ramps: Yes
  • Muzzle Device: PWS FSC556 Flash Suppressing Compensator
  • Barrel: 14.5” 1:8 Twist Modify Low-Stress profile .223 Wylde 41V50 CMV Barrel with FN HD Life Treatment
  • Muzzle Thread Pattern: 1/2"-28
  • Gas Block: PWS Long Stroke Piston System - 3-Position Adjustable Gas Block
  • Gas Length: Mid-Length
  • Bolt Carrier Group: PWS Long Stroke Piston Bolt Carrier Group
  • Charging Handle: Radian Raptor-LT Ambi Charging Handle
  • Weight:
    • MK1 MOD 1-M: ~4 lbs. 8 oz.
    • MK1 MOD 2-M: ~4 lbs. 4 oz.
  • Overall Length: ~23.5"


  • AR-15 lower receivers


  • 1x Primary Weapons Systems MK114 Piston Upper with .223 Wylde Barrel
  • 1x PWS Rifle Service Tool





If you’re ready to try a piston AR upper and you want a compact weapon without having to do all of the hoop-jumping associated with short barreled rifles, the Primary Weapons Systems MK114 is the upper for you. The PWS MK114 is built to respect the M4-type upper pattern and is field proven to be lethal at 500 meters with a number of different ammunition.

PWS MK114 Piston Upper

The PWS MK1 is the base of this and many other Primary Weapons Systems long stroke piston AR uppers. These uppers utilize a one-piece operating unit that consists of a floating piston head and bolt carrier group connected by an operating rod. Fewer individual moving parts equal fewer failures and performance that doesn’t hinge on excessive operator maintenance.

The PWS MK1 Mod 1 upper features an adjustable gas block, quality FNC Life HD treated components and the convenience of free-floating hand guards with built in Picatinny rail and quick disconnect attachments built in. The PWS MK1 Mod 1 is the upper of choice for the operator who wants to move toward a more reliable, modern system while maintaining the familiarity and assurance of a hearty feeling upper and forward assist.


The PWS MK1 Mod 2 is a more aggressive evolution beyond the standard AR upper. While it is still a quality forged upper, it has been given a facelift. PWS has been busy shaving excess mass away as well as removing the forward assist. With a weapon as reliable as the PWS MK1 Mod 2, there’s no need to retain it. A section of PWS’ own PicMOD® rail system has been added to allow the use of either Picatinny or M-LOK accessories without requiring obtrusive adapters. The result is a sleeker, more efficient upper that is ready to leap into the fray without holding you back with unneeded weight or unnecessary appendages.

Which version of the PWS MK114 you choose is up to you, either one will push your evolution beyond the competition, you just have to decide how far you’re ready to go. Primary Weapons Systems, Because It’s Time.

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