Rubber City Armory AR-15 Low Mass Competition Bolt Carrier Group
Lewis Creek Shooting School 02.25.14
There are those who are surprised when the subject of reducing the recoil of an AR-15 in 5.56 comes up. They assume that a .223-caliber 55-grain bullet couldn’t possibly generate enough recoil be a problem. This is true in hunting and slow-fire situations, but when you have to have a fast follow-up shot, as happens in 3-Gun and other speed-related shooting competitions, taming the recoil of an AR-15 becomes a really big issue.
The recoil that creates the problem is more a product of the operation of the rifle than the “strength” of the round it fires. In general, during firing the reciprocating mass of the rifle’s action generates a push-pull that moves the gun off-target. The lighter the rifle or carbine is, the more noticeable and pronounced this movement becomes.
3-Gun shooters have been working on this problem for quite a while, and it’s amazing just how recoil-neutral a good carbine or rifle can be. I recently reviewed the Colt CRP-18 and touted it as the best and most recoil-neutral AR I’ve ever shot. It is a very good competition gun. Shoot a normal AR of a similar weight and then the Colt, and you can see just how good. Most people I ask say that it feels like 75 percent of muzzle movement is reduced in the CRP over a standard AR-15 of similar weight.
On regular AR-15s, minimizing recoil is done by installation of a really good muzzle brake and adjustable gas block, and tuning the buffer system. The muzzle brake jets gas in a direction opposite the direction the rifle would normally move under the reciprocating mass of the bolt carrier. The adjustable gas block allows the shooter to tune down the gas flow to match the ammunition, feeding just enough gas into the bolt to operate it without slamming it back into the buffer. Tuning the buffer and spring smooths out the travel even further. The Colt CRP rifles and carbines come with all these modifications.
The only trick the Colt folks missed is lightening the bolt carrier. Lightening the bolt carrier allows the amount of gas pouring onto the action to be further reduced because there is less mass to get moving. Less weight is less inertia, and inertia is what gives the AR-15 its recoil. Enter the Rubber City Armory Low Mass Competition Bolt Carrier Group.
The Rubber City Armory Low Mass carrier is 25 percent lighter than a standard carrier. Chris Cerino is the operations director for Rubber City and on a recent visit to Lewis Creek, he brought a Rubber City Low Mass carrier to try on my Colt CRP-18. While it’s hard to improve on a really great rifle, Chris assured me the lightened carrier would make the CRP even better. We installed it and set about tuning the gas to match the lightened carrier.
Tuning an adjustable gas system is accomplished by reducing the amount of gas coming from the gas block until the bolt will no longer lock back on an empty magazine. You then open the system until the bolt locks back consistently, and you’re operating the rifle with the minimum amount of gas. Less gas means the carrier doesn’t slam to the rear and create a backward jump that disturbs your hold. Less gas also means a cleaner rifle, important with the direct impingement system of most AR-15s. The lighter carrier also contributes to less movement in the gun on the closing of the bolt as well. Since it weighs less, there is less forward slam when the bolt closes, so the secondary forward jump is also reduced.
On the Colt CRP Pro models, the adjustable gas system is externally adjustable with detent settings. With the Rubber City Armory Low Mass carrier installed, we reduced the gas setting by over two revolutions, a huge reduction in gas flow. Correspondingly, the stability of the rifle during double taps was even better. I honestly didn’t think the CRP could be improved, but the difference was noticeable. On a standard rifle, the difference would be shocking.