Thanks for the suggestions, they are spot on.
I think I can answer my own question now after more research. This is common problem with custom target chambers that are built tight to spec apparently. I polished a shellholder surface slowly by hand and kept trying to size the brass and chamber it. Took a while but I now have it working perfectly for a nice 'crush fit' of any brass I tried, .308, .243. or 7-08 R-P and FC. I wish I had thought to measure the base before I started to see how much I took off but it now is clearly labelled and will only go with those dies for that rifle. This should be a good shooter and there is some truth to Brownings claim that all barrels are hand chambered to precision target tolerances.
Have some ladder loads made up and can't wait to try it.
