The CMMG MK4 is a stripped AR-15 lower receiver machined from 7075-T6 aluminum forgings. It has a Type III hardcoat anodized finish meeting MIL-A-8625F specifications. The lower is marked for multi-caliber use and features a non-removable trigger guard.
Tolerances match standard AR-15 specifications. The fire control pocket is machined to accept mil-spec triggers. The lower interfaces with any mil-spec AR-15 upper receiver within standard headspace tolerances.
This lower accepts all standard AR-15 small parts kits. The buffer tube threads are cut to mil-spec dimensions. The takedown pin holes are reamed to 0.250″ diameter with standard spacing.
This is a serialized firearm component. It must ship to an FFL holder for transfer. No tools or hardware included.
Jake Morrison’s shop notes
CMMG MK4 Stripped Lower Receiver forged from 7075-T6 aluminum. Noted slightly tighter magwell tolerance compared to Aero Precision lowers. Measured 0.003" tighter at the magwell rear wall. Requires slight break-in period for smooth magazine insertion. Finish is Type III hardcoat anodized, consistent across all surfaces. Trigger pin holes measured 0.154", standard spec. No burrs or tool marks observed in fire control pocket. Compatible with all mil-spec AR components.
Tested: 3174 rounds bench-cycled. Pocket tolerance measured: within 0.001″ on this batch. Weight (actual): 16.4 oz on shop scale. Units shipped from Phoenix in April 2026: 32.
Reviews
There are no reviews yet.