I did a SBR build about two years ago.During the course of the build, I noticed the pin holes in the upper receiver did not perfectly line up with the push pins in the lower receiver. To get the rifle put together without sending the upper back to the manufacturer, I did a [span style='font-style: italic;']slight[/span] dremel job to open the front pin hole up in the upper so it would pin together.
The dremel job worked and the rifle works great.
I have noticed that if I push hard enough on the upper and lower from the side (while assembled and pinned) I get a tiny amount of movement at the front lug. My concern is that down the road this slight movement could damage my SBR lower by wearing it or causing cracks to form.
Should I just not worry about it, or is this a valid concern and should I replace the upper receiver with one that fits properly?
Pics of said SBR, ignore the circled area (that was from another thread long ago):