I know it's a hassle to pull the breechplug, but sometoimes that is the only way ti really see in that end. A hint before you pull the plug. Take a cold chisel and mark on the underside of the plugand the bbl near the center of the flat if there is room. This will help you get it back into the same place it was. Unscrew the plug check things out screw in the plug and line up the marks and you're done.
I just thought of someting else. there may be a screw thread or two beyond tight which can catch goo also. If it were mine I'd take the drum off first shine a bore light in there and look around...then take the plug out.
Hope this helps.