The MMR-556 is the first rifle we introduced in our line, and has continuously been our 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 our rifles, we use our M16 cut nitride bolt carrier group, matched with a fully nitrided Ballistic Advantage 16” mid-length barrel. Our mid-length gas system provides an extremely soft and controllable recoil impulse. We then paired these components with our tight fitting receivers, and ultra-rigid 15” M-LOK rail system to provide a rifle that is up for any task.

Our 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. Our fitted disconnector gives a positive, short reset that is hard to miss!

Out of stock


Out of stock

Forged Lower Receiver:

• 7075-T6 Forged Aluminum

• Cerakoted in Sniper Gray

• 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

• 30 round magazine

Forged Upper Receiver:

• 7075-T6 Forged Aluminum

• T-Marked Flat-Top with Picatinny Rails

• Cerakoted in Sniper Gray

• Mil-Spec Charging Handle


•Custombilt 15” MLOK handguard, Cerakoted in Sniper Gray

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

• 9310 Bolt

• 8620 Bolt Carrier