Smyth Busters: Should You Bed an AR-15 Barrel?

Brownells Gun Techs™ Caleb Savant and Steve Ostrem are back to put another firearm myth to bed, one way or another. Today's myth is that you can improve your AR-15's accuracy by bedding the barrel into the upper receiver. "You mean gluing it in place?" queries Steve. Actually, yes. The barrel extension usually fits into the receiver with a slightly snug slip fit. Proponents of "bedding" an AR-15 barrel use green Loctite® 294 to anchor the barrel extension in the receiver. These folks think bedding the barrel prevents it from wobbling, thus making their AR-15s more accurate.

This might help secure a particularly loose-fitting barrel extension. But under normal circumstances, a properly tightened barrel nut locks the barrel firmly in place. When the barrel nut is torqued down, the shoulder of the barrel extension is pressed tightly to the front of the receiver. Also, tightening the nut actually compresses the receiver around the barrel extension, almost like a collet. Some AR-15 manufacturers even make their upper receivers slightly undersized to obtain this extra-tight compression fit. BOTTOM LINE: Wobble or flexing of the barrel in the upper is normally not an issue.

If the barrel extension fits so poorly that after you tighten the barrel nut, it's still shimmying around like a dancer in a 1980s MTV music video, your upper is probably seriously out of spec. Rather than reaching for the green Loctite®, the better solution is to get a new, in-spec upper receiver.

If you do decide to bed your AR-15's the barrel, you might as well lap the receiver to get the straightest, cleanest possible metal-to metal fit. Brownells offers an Upper Receiver Lapping Tool for this purpose. But with most high-quality uppers, lapping is not necessary. (Ssshhhh! Don't tell the Marketing Dept. Caleb said that.)

So the myth that you should bed your AR-15 barrel is BUSTED. Bedding may have been necessary years ago when manufacturing tolerances on receivers and barrel extensions were looser. If you think you need to bed a barrel, you probably have other problems and should look into just getting a different upper receiver and/or barrel extension.