Luth-AR A3 Complete Upper Receiver Assembled 16in Lightweight Barrel 5.56mm 1-7 Twist 1/2 x 28 Thread A2 Flash Hider w/ Key MOD Palm Handguard Black. 5? M4 SOCOM profile barrel with F Marked Front Sight Base 5.56mm made from 4150 CMV steel with a 1-7?...