As of June 1st 2023, all pistols will be shipped with a bare “pistol buffer tube” in order to keep our customers clear of ATF rule 2021R-08F. Click here to read the rule.

The MMP-300 is our 300 AAC Blackout offering. We built our MMP-300 around the original intent for the 300 AAC Blackout cartridge. This short package is ideal for use with supersonic loadings, as well as subsonic suppressed loadings. These pistols are built to be the functional tool that the end user needs to meet and overcome any challenge.

At the heart of our pistols, we use our M16 cut nitride bolt carrier group, matched with a fully nitrided Ballistic Advantage 8” carbine-length barrel. Our pistol-length gas system provides an extremely soft and controllable recoil impulse. We then paired these components with our tight fitting receivers, and ultra-rigid 7” M-LOK rail system to provide a pistol 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!

We finish out our MMP-300’s with a four position SB Tactical SBA3 pistol brace, which is our choice for comfortable braced shooting.

Out of stock


Out of stock

Forged Lower:

• 7075-T6 Forged Aluminum

• Cerakoted in our 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 Spring

• Magpul MOE Grip

• SB Tactical SBA3 Stabilizing Brace

• Mil-Spec Safety Selector

• Magpul 30 Round PMAG®

Forged Upper:

• 7075-T6 Forged Aluminum

• T-Marked Flat-Top with Picatinny Rails

• Cerakoted in our FDE “peanut butter” colorway

• Mil-Spec Charging Handle


• Custombilt 7” MLOK handguard, Cerakoted in our FDE “peanut butter” colorway

Barrel (1:7 twist)

• 8””

• 4150 Chrome Moly Vanadium

• Nitride/QPQ Finish

• Thread: 5/8×24

• A2 Flash Hider

• Front Sight Block

•Carbine- Length Gas System

Custombilt M16 Cut Bolt Carrier Group:

• Properly staked

• Nitride Coated

• Laser Engraved Custombilt Logo

• HPT – High Pressure Tested

• MPI – Magnetic Particle Inspected

• 9310 Bolt

• 8620 Bolt Carrier