What's new

Bolt Lock Up for Rifle Accuracy


Jan 19, 2024
Reaction score
Trophy Points
Never too old to learn. How tight the bolt fits the barrel (in an AR the barrel extension) can affect accuracy. In Garands and M14 rifles the finished chamber is cut with a pull through reamer. Those are turned by an extension through the barrel with pressure put on by the bolt. You get very tight chambers that way.
you can do that in an AR. You buy a White Oak AR barrel pay the extra to get a matching bolt. They simply go through bolts till they find one that is tight. The bolts can vary as well as the barrels in tolerances. The barrel extension sets the headspace with the position of the index pin on the barrel. That can cart a great deal.
Found this to share.
10. Front/Back Bolt Play: If accuracy is the game, don’t leave a lot of front/back bolt play (keep it .003″ but no more than .005″). We’ve seen factory rifles run .012″ to .015″ play, which is OK if you need to leave room for dirt and grime in a military application. However, that amount of play is not ideal for a high-accuracy AR build. A lot of front/back bolt play allows rounds to be hammered into the chamber and actually re-formed in a non-consistent way, as they are loaded into the chamber.

Change in a bolt or bolt carrier group can change tolerances and bolt Lock up affecting accuracy. I once put a speed lock firing pin in a REM 700. They have a heavier spring to speed up lock time. It almost doubled the force required to open and close the bolt. As far as accuracy I never shot it. Steve Baldwin -fabulous guy who did the machine work for me on the rifle- recommended not too.
Anyway here is a great article on the accurate AR. One of the things I always do is face off the upper. It doesn’t take much to do it and insures good even torque on the barrel nut and more precise barrel reciever alignment, Again it is difficult to measure the improvement of doing so Unless you’re a testing agency. it Ain’t gonna compensate for a shit bargain basement barrel. 😂
That deal about epoxy on the upper/barrel assembly gives me the heebie jeebies. I’ve taken two epoxied uppers apart to salvage a great barrel for another hand guard set up and it wasn’t fun. But the gain in Accuracy may or may not be worth it. I don’t know. I just don’t want to do it. Lots of very accurate ARs aren’t epoxied.
Last edited: