Can Any AR-15 Upper Match Any AR-15 Lower?

Pairing AR-15 Upper & Lower Receivers

As a general rule, any mil-spec AR-15 upper receiver should fit any mil-spec lower without issue. It is not necessary to buy a matching upper & lower receiver set for your build unless you want those particular parts to match for aesthetic reasons.

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However, different manufacturers will have slightly different tolerances, meaning there could be a small amount of play between the upper and lower receiver. Poor fitment may range from nearly imperceptible to mildly inconvenient, but will most likely not have a noticeable impact when shooting.

Some Caveats With Lower / Upper Receivers

An egregious mismatching of parts or failure to assemble the upper / lower properly might result in performance issues. Otherwise, any negatives effects such as sub-par accuracy, shot placement, etc. are probably in the mind of the shooter.

As long as you conduct routine cleaning and maintain your rifle by replacing any worn parts, you can expect your build to last at least as long as any production rifle in your safe. Consider keeping a parts kit on hand for small repairs over the life of your firearm.

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Mistakes To Avoid When Building An AR-15

Are you about to embark your first AR build? Click here to browse all upper and lower receiver parts, and be sure to watch our video so you can avoid these common mistakes beginners make when building their first rifle.

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