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Primary Weapons Systems MK116 Piston Upper (16.1" 300BLK Barrel)

  • Primary Weapons Systems MK116 Piston Uppers (16.1" 300BLK Barrel)
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  • PWS 300BLK  MK116 Piston Upper - Mod 2
  • PWS MK116 Upper
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Primary Weapons Systems MK116 Piston Upper (16.1" 300BLK Barrel)

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$1,349.95 $999.95

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MPN: M116UB0B / 2M116UB0B


  • PWS long-stroke piston system - combines the agility of the AR-15 with the reliability of the AK-47 into a sleek and efficient design
  • 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: 300 Blackout
  • 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: 12.75-inch KeyMod Rail System - Made from 6061-T6 aluminum
    • MK1 MOD 2: 15-inch KeyMod Rail System with PicMod Technology - Made from 6061-T6 aluminum
  • M4 Feed Ramps: Yes
  • Muzzle Device: PWS FSC556 Flash Suppressing Compensator
  • Barrel: 16.1” 1:8 Twist Modified Low-Stress profile 300 Blackout 416R Stainless Steel Barrel (Black finish)
  • Muzzle Thread Pattern: 5/8"-24
  • Gas Block: PWS Long Stroke Piston System (Non-adjustable gas block. Adjustment know is for disassembly and cleaning only)
  • Gas Length: Mid-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. 5 oz.
    • MK1 MOD 2: 4 lbs. 1.7 oz.
  • Overall Length: 25.5"


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




Primary Weapons Systems brings the PWS MK116 300 Blackout Upper to the market for those of us who are ready to take a giant leap forward with a quality 300 Blackout piston system upper. The 16.1-inch barreled version of the PWS 300 Blackout piston upper allows for operation in a great number of varying operating environments and proves itself lethal out to the 500-meter mark with a variety of ammunition types. It has proven itself reliable in the field and is sure to impress those who are new to the advanced design of PWS’ long piston upper systems.

When engineers at PWS went to the drawing board to create the MK1 piston driven upper, the creative minds at Primary Weapons Systems sought to marry the legendary reliability of the AK-47 with the ergonomic advances and flexibility of the AR platform. If you try a PWS MK116 you’ll find that they have succeeded in creating an extra-reliable long stroke piston operated upper that adapts well to chambering in 300 Blackout and the variety of operating conditions.

Fewer moving parts and less susceptibility to the effects of fouling allows the PWS MK1 upper to work long after impingement systems have succumbed to wear, broken parts and the inevitable failures caused by poor maintenance. The MK1 upper relies on a single unit operating component created by connecting the Bolt Carrier Group to a Floating Piston with an Operating Rod. This creates a single moving unit from three parts that would be interdependent in function yet able to fail individually in previous generations of uppers. The reliable function of this system is less vulnerable to the effects of soot and other forms of fouling than its predecessors too. That frees you up to do the real work in the field rather than keeping your hands tied cleaning a firearm that isn’t happy unless it’s enslaved you in a cycle of eternal maintenance issues.

You have the option of choosing a more traditional looking PWS MK1 Mod 1 upper, which is a little heavier than the PWS MK1 Mod 2 and retains the forward assist that’s been left off of the Mod 2. The PWS MK1 Mod 1 is no slouch, with advanced features that leave competitors in the dust without taking the traditional AR fan too far from his comfort zone. If you like the confidence you get from the ritual of tapping that forward assist we're more than happy to oblige and wrap it up in a package with a piston operated 300 Blackout upper featuring free floated handguards with QD attachments and ample KeyMod Rail.

If you're ready to move even further ahead of the pack, let us suggest the PWS MK1 Mod 2. It's all that and exclusive PWS PicMOD® rail that accepts both Picatinny and KeyMod accessories. The receiver itself has been put on a diet, shedding excess ounces of material to the bite of the CNC while retaining its strength. The forward assist is also a thing of the past on the PWS MK1 Mod 2. Given the reliability of the long piston system, we're confident you just won't miss it.

Because It's Time. Strength Through Evolution. The Primary Weapons Systems MK116 300 Blackout.

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