E2 Armory Shows Off How Their Bolt Carrier Groups Are Machined

Each of the Bolt Carrier Groups seen in the video appears to go through a batch manufacturing process whereby several pieces are machined at a time to reduce the downtime usually associated with setting a new workpiece in. In my experience, I’ve also found that this technique allows CNC machinists to spot inconsistencies early on in the machining process even before the official quality control portion has begun.

• Bolt precision machined from 9310 alloy; carburized/case hardened & shot peened
• HP proof testing, 100% using a high pressure M197 or SAAMI commercial equivalent, without evidence of failure
• MPI testing after above, 100% inspection per ASTM E1444 using a standard 5 turn magnetizing coil with a current of 200 to 300 amperes. Circular and longitudinal continuous magnetization and a wet fluorescent solution shall be used. Conformance to MIL-STD-410 is required within ASTM E1444
• ultrasonically cleaned and Nickel Boron coating
• Markings laser engraved (HPT=High Pressure Tested, MPI=Magnetic Particle Inspection)
• Extractor, machined 4140 Tool steel alloy, hardened with Nickel Boron coating
• Extractor Pin, precision machined and ground AMS6440/52100 Bearing grade steel retaining pin
• Extractor Spring, 5 coil, ASTM Grade A 228 wire stock, stress relieved, Tensile Strength of 393,000 PSI Max, 80 Durometer Per AMS-R-6855 black insert
• Ejector, S7 shock resistant tool steel alloy, hardened, shot peened per ASTM B851/SAE AMS2430, manganese phosphate

• Ejector Spring, ASTM Grade A 228 wire stock, heat treated, stress relieved – Tensile Strength of 376,000 PSI Minimum
• Gas Rings, Steel Corrosion Resistant Per AMS 5906 – X3
• Carrier machined from 8620 alloy, full auto profile, heat treated, ultrasonically cleaned and Nickel Boron coating
• Gas Key machined from 4130 chromoly steel alloy, heat treated and Nickel Boron coating
• Socket Cap Head Screw, steel, grade 4037 per ASTM, heat treated & manganese phosphate 2x
• Gas Key is installed with Permatex aviation gasket sealer, torqued to 55-foot pounds, pneumatically steaked and break away tests performed to spec
• Cam Pin, precision machined 4340 chromoly steel alloy, heat treated and Nickel Boron coating
• Firing Pin, precision machined 8740 steel alloy, heat treated, precision ground & hard chrome plate
• Firing Pin Retaining Pin, carbon steel ASTM A510, heat treated & manganese phosphate
• All material, components and packaging made in the USA
• Price: $120.99