Fitting the Lug for Takedown Pin

I wasn't sure if this should go under Gunsmithing or not, so...

I did an AR build some years ago from an 80% lower. The rear pocket for the takedown lug was already milled in the lower so I didn't do any more work there, but the lug on the upper didn't want to fit the pocket. I chose to relieve the lug to fit the pocket. I have a non-zero number of additional lowers that are not fitting to their completed uppers in the same location.

Is it more highly recommended to fit the lug into the pocket or the pocket to accept the lug?

Inquiring minds...

That is weird that your upper isn*t working with your factory lowers. I would modify the one upper and not multiple lowers.

The Anderson 80% lowers are notorious for not machining the rear pocket enough for spec. Never asked why, but I guess that's why they have the nickname of "poverty ponies". I hit the front corners of the rear pocket now when I see one and the test upper and all the pre-built ones fit. I wouldn't consider machining the upper lug.