You may think that your AR-variant rifle already functions at the highest possible level of performance and reliability, but what if it turned out that you were wrong? The SureFire Optimized Bolt Carrier (OBC) is redefining what reliability is for AR rifles, especially those subjected to extreme round counts, and the test results are astounding.

SureFire OBC Optimized Bolt Carrier Group with SureFire buffer and SureFire spring
The SureFire OBC is a drop-in system that doubles the reliability of M4, M16 and AR-variant rifles. Its patented long-stroke design virtually eliminates bolt-over-base malfunctions. A new buffer and spring designed specifically for use with the OBC is also included.

A recent review by The Firearm Blog provides objective insight into the OBC’s performance and the innovations that set it apart from other Mil-Spec bolt carriers on the market. The author concluded his review this way:

“After testing the SureFire OBC for over a month, I can safely say it’s my favorite aftermarket BCG on the market. The $400 MSRP is a luxury for most AR-15 owners. Do you absolutely need it? No. Will you want it? Yes. However, for those complaining about a stale market for AR-15 accessories, this is the price of real innovation. SureFire did their homework on this one, and having Jim Sullivan design the OBC was a stellar move. So, would I buy one of these? Absolutely, and now I feel I need 4-6 more of them. Because honestly, it’s all I want to shoot now.”

As the author points out in the review, the OBC was created by SureFire in collaboration with firearms industry legend Jim Sullivan, the designer of the M16. The OBC’s success lies in innovative design and superior engineering that address the common shortcomings of standard Mil-Spec bolt carrier groups. Its patented design doubles the reliability of your M4/M16/AR rifle during suppressed or unsuppressed full-auto or semi-auto or firing full-auto.

The key to this remarkable reliability increase is the way the OBC reduces the cyclic rate and delays the unlocking of the bolt during the cycle of operations. The cyclic rate of standard Mil-Spec bolt carriers is about 850 rpm when firing unsuppressed, and it can run beyond 1000 rpm when a suppressor is used. At these high cyclic rates, bolt-over-base malfunctions are a common issue with M4/M16/AR rifles. This malfunction occurs because the bolt travels forward before the magazine spring has enough time to position the next round for feed. The bolt goes past the base of the cartridge and pushes it forward from the stack at an odd angle, prompting the rifle to stop running. This can be a complicated malfunction to clear for both experienced and novice shooters alike, as it will damage the cartridge and render it unfireable.

The SureFire OBC eliminates bolt-over-base malfunctions by pausing the BCG at the open position. The OBC’s long-stroke design incorporates a shortened gas carrier key in conjunction with a shorter buffer. This allows for a 60% increase in stroke length, which translates into two significant improvements: 1) it results in more clearance past the magazine, giving it more time to present the next cartridge for proper feeding, and 2) it increases momentum, reliably feeding rounds in adverse conditions. Other innovative and purpose-driven features include a lengthened cam pin slot, which keeps the bolt locked longer during the “unlocking” phase. This allows gases more time to exit the bore, lowering chamber pressure by 15%. This not only reduces incessant wear on components but also subdues back pressure and gases exiting the ejection port.

Additionally, the OBC incorporates a spring-loaded neutrally balanced counterweight that works three distinct times in the cycle of operation: First, the counterweight delays unlocking as the bolt begins its initial movement during the unlocking phase. Then, at the most rearward point of travel, the counterweight keeps the entire OBC in place, much like a dead-blow hammer, for additional time (again allowing more time for reliable feeding of ammunition from the magazine). And finally, the counterweight improves carrier and barrel extension lock-up in the locking phase, eliminating bolt bounce.

Extreme reliability is the real benefit of the OBC, but it isn’t the only one. It also contributes to a higher degree of controllability when used on fully automatic weapons due to the lowered cyclic rate. And it smooths out the recoil impulse, which allows better tracking of sights.

The SureFire OBC comes as a complete drop-in package that includes the optimized bolt carrier group, a unique buffer, and custom buffer spring. The steel alloy-constructed bolt carrier is also coated with an advanced coating that resists friction during use and simplifies cleaning. Every SureFire bolt is magnetic particle inspected after firing a proof round to ensure that it meets our high durability standards. The OBC is the absolute pinnacle of bolt carrier design, performance and reliability.

You may have thought your AR is as reliable as it can be, but the man who designed it would say otherwise.

For more information on the SureFire OBC and the full lineup of the world’s finest — and most innovative — illumination tools and tactical products, visit