If that is indeed the problem.
I like to use candle soot to blacken the area, actually I have an oil lamp and turn the wick high so I can get a sooty flame. Some guys use lip stick.
Get the soot all over the end of the barrel, then try to install. Then the place where it's rubbing on the frame will show up, the soot will rub off.
You should find where it's stopping before removing any more metal.
It's easy to file metal away, but difficult too UN-file.