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  • Post last modified:January 17, 2024

In this ultimate build guide, we put together a complete MK18 parts list for anyone building a SBR (NFA) or a pistol (non-NFA). 

For around approximately $1500, you can build a bad ass MK18 with exact parts you want, and you can also upgrade it  later.

Disclosure: All products have affiliate links for earning commission to support the website when you purchase

ddmk 18 with vortex uh1 gen 2

MK18 Lower Receiver

Also be sure to check out our best AR15 drop in trigger guide for more

Most receivers are made at the same machine shop, the difference is that the brand logo determines the price you pay.

MK18 Upper Receiver Build

dd mk18 surefire m300 light

Buy Factory MK18 Rifle Parts

Daniel Defense MK18 Upper RIS II

DDmk18 upper
  • Battle proven 6 bolt bolt-up system securely attaches the handguard to the upper receiver
  • 2 piece design accepts M203 grenade launcher without additional parts
  • Seriously made for war
  • 6061 T6 aluminum, durable & lightweight
  • Free float system, increases accuracy
  • Continous top rail

PSA 10.5" 5.56 NATO MK18 Upper Clone

PSA 10.5 upper

The Palmetto State Armory 10.5" 5.56 NATO upper is another great option to clone a MK18 style rifle. The upper features forged 7075 T6 mil spec aluminum with hard coat anodized for durability and corroision protection. 

Yes it comes with a bolt carrier group. All for under $400

MK18 Mod 3

Mk18 mod 3 upper

The MK18 MOD 3 is about having a 11.5" barrel and the MK16 rail & better suppressor performance. The US Army calls it the MK18 CQBR UGRI.

The upper is improved to prevent gas blow back in suppressed mode, the MK18 Mod 3 also comes with the PRI M84 charging handle.

MK18 MOD 0 

mk18 mod 0 upper

The MK18 Mod 0 was one of the earliest configurations based on the M4A1.

It was simply a shorter M4A1, and it features the classic KAC M4 quad rail plus the fixed A2 front sight post.

If you clone this upper just for the aesthetics, it's quite simple. You can buy affordable Aero Precision 10.5 complete upper then change the rest as you desire or build from scratch:

KAC RAS quad rail

KAC rail cover

Colt 10.5" barrel assembly 

FSB gas block

Required MK18 Build Tools

ar15 loose fit barrel in upper receiver

We highly recommend using these tools to assemble the upper receiver at home, or take it to a gunsmith.

Midwest Industry Reaction Rod - It prevents receiver shear while torquing barrel nut and muzzle 

Vice Clamp (Heavy) - Holds everything in place on a work bench 

Work Bench - Must be able to handle torque (Recommend something sturdy)

1/2" Drive Torque Wrench (Ft lb) - Use to apply exact torque