It is permissible to slightly radius the sharp edge (if that is there) on the rear of the chamber mouth. Just slightly, to help guide the bullet in & not shave brass from the ctg case.
So, you are saying with only 4 in the magazine, it feeds properly with RN's? If so, no need to load 5.
With open sights, blunt round nose bullets will handle any range you are likely to need & handle them better than pointy bullets, imho.

Welcome to the forum - a nice introduction.