LANTAC 556 MILSPEC+ BCG BLK NITRIDE

Description

The Lantac M-SPEC BCG is built for shooters who want a reliable, properly spec’d bolt carrier group without compromising on materials or finish — whether they’re assembling a first AR build or replacing a worn component in a working rifle. It fits standard AR-15 pattern uppers chambered in 5.56x45mm NATO or .223 Remington.

The carrier is machined from 8620 steel, then case hardened and hard turned so that internal dimensions hold true to military specification. That precision matters at the carrier key and bolt tail, where loose tolerances bleed gas and degrade reliability. Rather than the conventional Type M phosphate coating, Lantac applies a QPQ Nitride finish — a thermochemical surface treatment that penetrates the metal rather than sitting on top of it. The result is a harder bearing surface that resists corrosion more aggressively and wipes clean more easily than phosphate under sustained use.

The bolt itself is cut from Carpenter 158 steel and shot peened using S110 shot, with intensity verified by an Almen gauge A-2 strip at .006–.008. Shot peening compresses the surface layer of the metal, which resists the fatigue cracking that eventually shows up at the bolt lugs and cam pin hole under repeated firing cycles. The carrier profile is full-auto, meaning it carries more mass than a commercial-spec carrier — that additional weight moderates the bolt’s rearward velocity and can smooth out the impulse when running suppressed or with higher-pressure ammunition.

Lantac fits each M-SPEC with their CP-R360 cam pin, machined from 17-4PH stainless steel, hand polished, and hardened to H900 condition. The domed geometry reduces the contact patch between the pin and the carrier channel, which lowers friction during the rotation cycle. The M-SPEC ships with a lifetime warranty from Lantac USA.