The Primary Weapons Systems MK116 Mod 2-M Complete Upper (brand part number MK1-M2U-223-16) is a 16.1-inch AR-15 upper cut in the .223 Wylde chamber for reliable feeding across both .223 Remington and 5.56 NATO ammunition. PWS builds the MK1 Mod 2 line around its long-stroke gas piston system, an operating system that keeps combustion byproducts out of the receiver for cleaner, more reliable cycling than a direct-impingement upper. At 16.1 inches, the barrel clears the federal rifle barrel-length minimum, so this upper carries no SBR caveats regardless of what lower it is paired with. Cut with a 1-in-8-inch twist rate, this complete upper is finished in black and ready to mate to a compatible AR-15 lower receiver.

Key Specifications

• Chambered in .223 Wylde, accepting both .223 Remington and 5.56 NATO ammunition.
• Barrel length is 16.1 inches, clearing the federal rifle barrel-length minimum.
• Rifling twist rate is 1-in-8 inches.
• Sold as a complete upper assembly.
• Part of the MK116 Mod 2-M line from Primary Weapons Systems.
• Finished in black.

Frequently Asked Questions

Does this upper include a lower receiver? No, this is a complete upper assembly only; the buyer supplies a compatible AR-15 lower.

What ammunition can I run in this upper? Both .223 Remington and 5.56 NATO, thanks to the .223 Wylde chamber.

Is a 16.1-inch barrel restricted by NFA rules? No, it clears the federal rifle barrel-length minimum, so there is no SBR concern on any AR-15 lower.

Buy the PWS MK116 Mod 2-M Complete Upper

Order the PWS MK116 complete upper from our Lubbock, Texas gun shop for fast, insured shipping. See the full lineup of Primary Weapons Systems AR15 uppers for your build.