308 Bolt Carrier Group Guide

The 308 Bolt Carrier Group is one of the most confusing aspects of the 308 AR platform. Unlike the AR-15 there is no mil-spec 308 Bolt Carrier Group. While it is possible to make some of the competing designs work with each other we do not recommend that path. Lets simplify things somewhat.

• You can only use an AR-10 Bolt Carrier Group in an Armalite AR-10 Rifle!

• You cannot is an AR-15 Bolt Carrier Group in any 308 AR or AR-10!

• You can only use a Rock River Arms RRA LAR-308 Bolt Carrier Group in a RRA LAR-308 Rifle!

• You can only use a DPMS GII Bolt Carrier Group in an DPMS GII Rifle!.

• You can only use a DPMS LR-308, 308 AR Bolt Carrier Group in 308’s based on this 308 platform!

Additional 308 Bolt Carrier Group Details

DPMS LR-308, 308 AR Bolt Carrier Groups are the most common 308 BCG’s available. Unfortunately some manufacturers and vendors refer to them incorrectly as AR-10 Bolt Carrier Groups. (See the first bullet above). If the specifications do not actually specify DPMS LR-308/SR-25 contact the manufacturer for clarification. Sometimes a manufacturer will be more specific on their rifle pages. Do not risk your personal safety by using the wrong 308 bolt carrier group. Know you hardware!

308 Bolt Carrier Finishes – Bolt Carriers are available in a multitude of finishes such as phosphate, hard chrome, titanium nitride and nickel boron to name a few. Research and get what best suits you particular application. My personal preference is for hard chrome. Its what I use on all my gas guns.

308 Bolt Carrier Lubrication – While I’m an advocate for high tech lubricants in firearms I have found inexpensive Mobil 1 to work extremely well on the 308 AR Bolt Carriers. I also suggest initially running the bolt carrier pretty wet with lubricant. These rifles tend to be a little tight when new. A word of caution, be careful not to let a measurable  of oil in the chamber as it could affect proper chambering of a round.

Sharing a Bolt Carrier –  It’s not advisable to use one bolt carrier group in more than one rifle. The bolt and barrel extension mating surfaces polish and wear together. Using the same bolt in more than one rifle can at minimum accelerate wear between the bolt and barrel extension. The worst case scenario is an unsafe condition from an improperly mated or worn bolt and barrel extension.

Headspace – As mentioned previously there is no milspec. Manufacturers are producing 308 bolt carrier groups to there own specifications and tolerances. Get some headspace gauges and avoid personal injury.