Dark mode is

Product Unavailable

Unfortunately, the following product is currently unavailable through Rainier Arms.

Custombilt Firearms MFG MMR-556-C 5.56 NATO Rifle - 16" FDE

AR-15 Rifle


The MMR-556 is the first rifle Custombilt introduced in their line, and has continuously been a best seller. These rifles are built to be the functional tool that the end user needs to meet and overcome any challenge. 

At the heart of their rifles, Custombilt uses their M16 cut nitride bolt carrier group, matched with a fully nitrided Ballistic Advantage 16” mid-length barrel. Their mid-length gas system provides an extremely soft and controllable recoil impulse. Custombilt then paired these components with their tight fitting receivers, and ultra-rigid 15” M-LOK rail system to provide a rifle that is up for any task.

Their MPP-GI trigger has micro polished contact surfaces, and a fitted disconnector. This combination gives you the 5lb weight of a typical duty trigger, and removes all of the gritty drag while breaking the shot. Their fitted disconnector gives a positive, short reset that is hard to miss!


Forged Lower Receiver:

  • 7075-T6 Forged Aluminum
  • Cerakoted in their FDE “peanut butter” colorway
  • Upper Receiver Tension Screw with nylon tip to remove any slack between lower and upper receiver.
  • Detent Set Screw for rear take-down pin (captures spring that is normally held in by the end plate.)
  • Bolt Catch Screw (Used in place of the Bolt Catch roll pin)
  • Custombilt MPP Trigger: (Micro Polished Performance) GI Trigger
  • Custombilt Enhanced Trigger Guard
  • 6-Position Mil-Spec Buffer Tube, Carbine Buffer, Stainless Steel action Spring
  • Magpul CTR Stock
  • Magpul MOE Grip
  • Mil-Spec Safety Selector


Forged Upper Receiver:

  • 7075-T6 Forged Aluminum
  • T-Marked Flat-Top with Picatinny Rails
  • Cerakoted in their FDE “peanut butter” colorway
  • Mil-Spec Charging Handle



  • Custombilt 15” MLOK handguard, Cerakoted in their FDE “peanut butter” colorway


Barrel (1:7 twist)

  • 16"
  • 4150 Chrome Moly Vanadium
  • Nitride/QPQ Finish
  • Thread: 1/2 x 28
  • A2 Flash Hider
  • Low profile 4140 nitride gas block
  • Mid- Length Gas System


Custombilt M16 Bolt Carrier Group:

  • Properly staked gas key
  • Nitride Coated
  • Laser Engraved Custombilt Logo
  • HPT - High Pressure Tested
  • MPI - Magnetic Particle Inspected
  • 9130 Bolt
  • 8620 Bolt Carrier


Weight: 6.7 lbs

Includes: (1) Lancer 30rd Magazine

More Information
Product Type AR-15 Rifle
Manufacturer Custombilt Firearms MFG
Thread Pitch 1/2x28
Twist Rate 1:7
Color Flat Dark Earth
Gas Length Mid
Barrel Length 16"
Caliber 5.56 NATO
Google Customer Reviews Google Customer Reviews