Lapping upper receiver

I have a few aero precision upper receivers and my ?? is do I need to lap them or does it matter?

I would lap them, there is always a little bit of an issue. I think it helps the barrel nut seat better anyways, anything that makes the bolt lock and release better eliminates future problems.


Why would anything need lapping? I’m lost on this.

It eliminates canting of barrel extension in receiver.


I started doing it on all my builds and have yet to find an upper regardless of make that doesn’t need it to some extent, just some more than others


Does the factory do this before shipping? QC…