Overpressure!

[MtnMike2]

I bought an E. A. Brown barrel in .270 Winchester for a T/C Encore years ago. It's a heavy barrel, made for target shooting. However, I don't have any target-only rifles and came to the conclusion years ago that I want all my loads to be hunting loads. I started reloading for rifles about 6 years ago. This barrel has always been a slight problem. I would work on loads for it, get discouraged or distracted by loads for my other rifles and forget about it for a while. But there's always been some problem when I came back to it. In the last couple of years I've become more aware of high pressure signs and been paying more attention to them. I noticed that some of my old .270 loads showed signs of high pressure - primers cratering, etc. Most recently, I reduced the load for 130 grain Sierra GameKings to the "most accurate" load, not the max and made the OAL .005" shorter than Sierra recommends but consistent w/ Lyman. Took them to the range yesterday. First shot, primer spread out flattened and blackened the outside of the bottom of the case. I put it away immediately.
I noticed when cleaning it last night that a .270 jag with a wetted rag won't go down the barrel, so I used a smaller jag (6.5 mm?). Could this barrel be out of spec? or tighter than most .270s? Maybe it has to do w/ rate of twist? Should I attempt to contact the manufacturer E.A. Brown ?


Thanks in advance,
Mike