Combating AR-15 Bolt Carrier Tilt

Taking baby steps to correct an accuracy short fall in AR-15 rifles.

by Joe Carlos

Eugene Stoner never designed his AR-15 to be a tack driver. It was intended to be a lightweight battlefield weapon but by good fortune it happens to be easier to work on than its predecessors. In spite of certain design elements, it is far more accurate than it has any right to be. With just a little bit of work, ARs can be made to perform nearly as accurately as expensive custom bolt rifles.

In order to shoot tight groups with any Stoner platform, the custom gunsmith has to correct certain elements of the rifle’s design. Among them are tightening the fit of the upper to the lower and making the barrel extension more rigidly stabilized in the upper receiver. Getting uniform bolt lock up and consistently positioning the chambered cartridge is next. I have written a number of detailed articles for American Gunsmith covering this and more. In order to fully integrate the material that follows here, it would be prudent to review this. For example, it makes little sense to correct bolt carrier tilt if it just throws the gas tube out of alignment. Those occasionally building a Stoner rifle for single round feeding only should review information and options on neck dimensions in their chamber selection and conducting magazine checks on precision rifles feeding normally.

Although I and other gunsmiths have known about how bolt carrier tilt degrades accuracy in Stoner platforms for decades, the first time I mentioned it in this magazine was near the end of “AR-15 Upper Quick Fixes: Match Bolt Carriers” in the May 2014 issue. I have talked to gunsmiths and industry folks who actually knew Stoner that knew about this issue while my younger self was running around the jungles of Viet Nam with an early XM16E1.

Why is bolt carrier tilt a problem?

Read more in the May 2017 issue.

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