Caliber:  5.56 NATO Barrel Length:  16 inches Barrel Profile:  M4 Barrel Steel:  Chrome Moly Vanadium Barrel Finish:  Phosphate Chrome Lining:  No Muzzle Thread Pattern:  1/2" x 28 Twist Rate:  1 in 8" Barrel Extension:  M4 Gas System Length:  Carbine Diameter at Gas Block:  .750" Gas Block Type:  F-marked Front Sight Base Muzzle Device:  A2 -style Receiver Material:  Forged 7075-T6 Receiver Type:  M4 Handguard Type:  M4 with heat shields Bolt Material:  Carpenter 158 Steel Bolt Carrier Profile:  Full Auto Fire Control Group: Panther Polished Trigger (PPT) Grip:  A2-style Stock:  M4-style Buffer Tube Length:  Carbine Buffer Tube Diameter:  Mil-spec Overall Length:  32 inches Weight (as configured):  6.8 lbs Backup Sight: Magpul MBUS Rear Sight, Black