I generally just read and let those who know this stuff do the posting but this one hit a nerve as I'm in the other end of the same boat your in. My circumstance involves 6BR Lapua nk up to 7br, I know NO one ever has a problem with this "but" in my case .3075 loaded round and .3095 fired case from .310nk chamber is a problem. problem however is the throating length which was designed for 130MK not the 162 that I shoot, putting the base of bullet dead on under the neck- shoulder doughnut area. Original fix was to ream with .285 reamer as fired cases had good feel with the .284 mandrel in a K&M set up. Ordered a throating reamer from Pacific and did it without any of above, few turns and no more doughnut problems. If Hunter gun differant line of approach may be necessary.
Don't give up, It can get worse!
Carroll