Complete lower receiver assembly for AR-15 style rifles manufactured by Primary Weapon Systems (PWS). The MK1 MOD2-M receiver features ambidextrous controls and a mil-spec enhanced trigger. The included PWS MOD 2 Enhanced Buffer Tube uses a ratchet-lock castle nut to eliminate the need for staking and features an extended anti-tilt lip to ensure smoother cycling by preventing the carrier from bumping the front of the tube during the action cycling. The receiver group also includes a BCM Mod 0 buttstock along with a Mod 1 pistol grip. This receiver is multi-caliber rated and is compatible with most mil-spec upper receiver assemblies.