American Tactical Imports Omni Hybrid Stripped AR-15 Lower Receiver Multi-Caliber Reinforced Polymer

The Ruger AR-556 is an affordable, American-made modern sporting rifle with the rugged reliability that you have come to expect from Ruger. The cold hammer-forged 4140 chrome-moly steel barrel with ultra-precise rifling provides exceptional accuracy, longevity and easy cleaning.
Specifications:

Rifle-length gas system
SBN treated threaded barrel & low-profile gas block
Ruger® muzzle brake with radial port design
Slim, free-float 15″ handguard with M-LOK® slots at the 3/6/9 positions with additional slots on angled faces near muzzle
Gas operated, semi-auto
Type III hardcoat anodized 7075-T6 aluminum flat top upper receiver with forward assist, dust cover & brass deflector
9310 alloy steel bolt, shot peened & pressure tested
Cold hammer-forged chrome-moly steel barrel with matte black oxide finish & ultra-precise rifling
1:8″ twist rate
M4 feed ramps
Enlarged trigger guard