SureFire’s new Advanced Rifle Operating Core is a system consisting of an enhanced Bolt Carrier Group, Barrel Extension, Buffer and Spring.
Because AROC requires a new Barrel Extension, they’ve also developed a Drop-In BCG called the Optimized Bolt Carrier. It includes Buffer and Spring. Although it’s not fully optimized like AROC, it is backward compatible with existing Mil-Spec AR pattern rifles.
Below, you can see (top to bottom) the AROC, OBC and standard AR BCGs.
The AROC Bolt offers 30% longer bolt lugs. Naturally, this means it requires a longer Barrel Extension. This was done to eliminate bolt lug breakage.
Additionally, the Buffer is longer than the Mil-Spec version. The H8S comes with AROC and is 8 oz. The 2 oz H2S comes with the OBC. The included Action Spring offers additional tension.
Regardless of which SureFire BCG, the Gas Key features a single screw which SureFire’s Barry Dueck related is stronger than the standard two screw model.
The BCG features an internal weight which is spring loaded in both directions. This, along with the other elements, combine to offer additional travel time. This also affects the angle from the bolt to the feed ramp. With a standard M4, the angle is 52 Deg. For an M16A4, it’s 45 Deg. But with AROC, it’s 37 Deg.
When the Bolt is at the end of its stroke while using a Mil-Spec BCG, it takes 28 milliseconds for the bolt to travel back into battery. With AROC, it’s 38 milliseconds. That slight difference is signifigant, especially when firing full auto or suppressed, or both.
On the range, AROC was demonstrated successfully with both Piston and Direct Impingement rifles. Although we previewed a version of this at 2016 SOFIC, SureFire has been working with suppliers to bring the cost down signifigantly from the initial estimates. At this point, Bolt Carrier Groups are a commodity item. Prices are so low that even specialized versions, such as this, have to be price competitive as possible.
No word yet in when this will be released commercially.
