Perhaps a rather trivial question but,
I just got my bushy m4gery upper,  to put on Preban olympic lower.
When rotating upper into  the lower it binds at the corners of the "insert tab, where the 2nd pin hole is"

Do I
1. grind on the brand new upper to make it fit my lower.  (I hate to mess up the nice finish.)
2.   Widen the inside of the lower which is more difficult and "cuts" the preban part.
3.  Quit asking stupid question and grind away on wherever it takes.
Thanks

well if your going to grind something grind the upper!! dont grind the lower since it worth alot more

if it fits with other uppers   trim the upper....    trim the upper

Thanks.
Just took a bit of trimming and she's snug and in place.