Invented by Jim Sullivan, one of the original designers of the M16, the SureFire Optimized Bolt Carrier (OBC) is designed to improve the functionality of an M4/M16/AR variant weapon system during both unsuppressed and suppressed firing. This patented design makes numerous improvements to the standard Mil-Spec full-auto bolt carrier group which allows more time for reliable feeding of ammunition from the magazine, nearly eliminating bolt-over-base malfunctions. The OBC also delays unlocking of the bolt during the firing sequence, which allows expanding gases more time to exit the bore, in turn reducing back-pressure gases exiting the upper receiver group. Additionally, the neutrally balanc Mfg: Surefire