Breach plugs are like nipples they burn the hole out a little each time you fire them. I know there are some people here that either don't seem to understand that or choose not to admit it for their own reasons. I have had to replace the breach plug in my Omega before it was 6 months old; I heard there was a batch that was not to good.
And remembering that I shoot as much in 6 months as some people do in a life time. Any way the two things you mentionare normally related to that problem if you have a set of calipersfind some thing that fits the hole snug and measure. A new one is 25 thousands and if its as big as a number 60 drill then in my opinion its too big.
As was mentioned above there are several primers that will coat the area with a black residue thatdoes notmean any thing except how dirty your primer is. Hope this helps. Lee