Mike Matteson
Well-Known Member
Due the math for the bushing size. You'll need the neck wall thickness x 2. Plus bullet OD added together less .002 for neck tension, should be your bushing size. The only problem is that the thickness may vary some from case to case. In the past I have found the different brands of brass the thickness is different from case to case. I found that in cutting necks to thickness. Now I cut all my neck to a thickness to start with. So that part of my formal for bushing size. I do this with new brass to start with. I don't use a mandrel to shape the inside of the neck to push the irregularity to the exterior of the neck after sizing. Not need after the neck has been cut. So that cuts down the working of the neck to set neck tension and moveing the irregularity of the neck thickness to the outside of the neck. annealing after each firing. Possible either not ennealing enough, or chamber size to big, plus working your neck part of the brass to much. As far as your primer goes I don't see anything wrong there. Picture enlarge is hard to tell any great detail.
You could also try some other brass manufacture brass to see how they hold up. To see if the problem carry on with the different type of brass.
This is how I figure the bushing size. Bullet OD .0308 + Neckness of ? or I'll use .015" per side x 2 for .03. So I have .308+.03-.002 for neck tension. Equal 0.336 bushing size. I believe my math is correct.
So it looks to me you are undersizing the neck by about .009".
You could also try some other brass manufacture brass to see how they hold up. To see if the problem carry on with the different type of brass.
This is how I figure the bushing size. Bullet OD .0308 + Neckness of ? or I'll use .015" per side x 2 for .03. So I have .308+.03-.002 for neck tension. Equal 0.336 bushing size. I believe my math is correct.
So it looks to me you are undersizing the neck by about .009".