There are things that make their presence known only by their absence. Often, it's an unexpected small thing, like an endplate.

Today, I swapped a carbine RE on Colt 6920 for an VLTOR A5 and reinstalled the carbine RE on another lower. A straight forward job that went without a hitch. Big deal, right? As it turns out, yes, it is.

My previous experiences with installing and removing REs involved generic brand parts. The problem I ran into was with the fit of the tongue of the endplate in the groove of the RE. The fit was loose and when tightening or loosening the castlenut, care had to be taken so the RE wouldn't spin. If the RE turns while tightening the castlenut, the RE will be off angle and the tongue will damage the threads of the RE. Both create a disturbance in my CDO.

My experience with removing and installing the Colt and VLTOR REs was different. The fit of the tongue of the endplate in the groove of the RE was much tighter. The fit prevented the RE from turning making it easy to install without damaging the threads and ensuring the RE was properly aligned.

Parts are parts but only if they are made to the proper specs. I thought the poor fit between endplate and RE was normal. If I hadn't worked with endplates and REs made to the right dimensions, I never would have known otherwise.

In case anyone is wondering, a Colt 14.5" Socom barrel will not lock back with a 5.3 oz A5 buffer. It will fire, extract and eject, but it won't lock back unsuppressed. It will lock back with a suppressor