Lantac M-SPEC® Above Mil Spec. The Lantac M-SPEC® 5.56/.223 BCG is precision machined to milspec dimensions and tolerances. The carrier is full auto style with increased mass and is manufactured from 8620 steel, case hardened and hard turned/ground so that internal dimension are exact to mil specifications. It is then QPQ Nitrided rather than Type M Phosphated to give increased corrosion resistance, durability and performance. The Bolt is machined from Carpenter 158 or 9310, shot peened and hard turned as per the military spec. Each BCG is further fitted with a Lantac CP-R360 domed head cam pin, which are precision machined from 17-4PH stainless steel, hand polished and hardened to H900 condition, this further reduces friction and wear within the upper receiver. The M-SPEC® line of products are ideal for budget builds where quality and reliability are still paramount.8620 Carrier, Heat Treated, Hard Turned & Ground.MPI Carpenter 158 or 9310 Bolt, Shot Peened, Hard Turned / Ground.QPQ Nitride Finish.CP-R360 Domed Cam PinShot Peening is conducted with S110 shot, Established by Almen Gage A-2 strip .006 -.008