LiveLife
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Any chance that separate "taper crimp" die is Lee Factory Crimp Die (FCD)?john16443 said:experiencing significant keyholing ... about 30% of the time.
I use a separate taper crimp die on my last station to reach 0.375 to 0.377".
1. At this point, my "probable" guess would be that the bullet is undersized to the barrel and the bullet base is not obturating enough to seal to the barrel and the high pressure gas is leaking unevenly as the bullet is exiting the barrel to cause the bullet to tumble.
2. Also, could you measure the case necks of several finished rounds to see if they are completely circular? (to rule out if the taper crimp die is deforming the bullet out of round - this would cause uneven escaping of high pressure gas as the bullet leaves the barrel).