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The CMMG Mk3 Carbine Receiver Extension and M4 Stock Kit includes 6-position M4 buttstock, CMMG 6-position mil-spec Receiver Extension (Buffer Tube), Buffer Tube Castle Nut, Receiver Endplate, .308 Carbine Buffer, and .308 Carbine Action Spring.
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A comprehensive overview of every major component in an AR-15 build—including what's inside bolt carrier groups and parts kits—organized by assembly for new builders.
12 min read
Guide
A neutral overview of AR-15 buffer systems, covering carbine vs. rifle receiver extensions, buffer weights, springs, and how these parts affect cycling and recoil.
5 min read