What is receiver lapping?

Upper receiver/barrel alignment is critical for accuracy. Lapping the receiver ensures a perfectly square and true surface for the barrel to mate against.
This produces:

  • optimal positioning of the barrel nut so ideal torque can be achieved
  • ensures barrel and handguard/rail are properly aligned
  • makes “timing” of the barrel nut easier
  • proper gas tube hole alignment through the barrel nut and receiver holes
  • helps align front and rear A2 style sights (or other barrel mounted front sights)
  • helps align gas bocks with picatinny rail segment

Does it work?

From what we observed, yes it does. It’s a simple solution to a problem many of us never realized we had.

We had an upper where the gas tube was clearly sitting a fraction of an inch closer to one side of the interior of the rail than the other thus preventing proper insertion of the gas tube into the receiver.  After first verifying the gas tube was properly installed and seated into the gas block, we used the lapping tool on the upper.  After lapping the upper receiver the gas tube sat perfectly dead center.  Having seen this firsthand, we now use it to square all of our upper receivers.

How long does it take?

The lapping process typically take no more than 10 to 15 minutes per upper receiver.

Perfection is not attainable,
but if we chase perfection we can catch excellence.
Vince Lombardi, American football coach

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