Quick Tip: Setting Up a Lightweight Bolt-Carrier Group

Lightweight AR-15 bolt-carrier groups are becoming increasingly popular. But there are some persistent misconceptions about them that lead folks to set up their rifles incorrectly and not get the benefits they wanted from a lightweight BCG. Brownells Gun Tech™ Caleb Savant - who's by no means a lightweight! - explains that a standard bolt-carrier group has a lot of "extra" metal in it. Some of that metal can be removed to reduce the BCG's weight, and it will still do its job correctly. A lighter bolt-carrier group has LESS reciprocating mass, so it operates at a HIGHER velocity. The big benefit is a SOFTER recoil impulse. Combine it with a lightweight receiver and barrel, plus an effective muzzle brake, and you have a gentle-recoiling, lightweight rifle that's really pleasant to shoot. Sounds great, right? What could go wrong? If the bolt-carrier group's velocity is too fast, the rifle can malfunction. So some folks swap in a heavier buffer to slow down the lightweight bolt-carrier group - which totally defeats the whole purpose of the faster-moving lightweight BCG! How do you reduce the BCG's velocity enough to keep the rifle cycling reliably while also enjoying lighter recoil? Install an adjustable gas block and reduce the gas flow so you have just enough to operate the bolt reliably.