8x58R problems

[mm1ut1]

Got some 40/65 Winchester brass sized down from 45/70. Spent the day turning the rims down to fit the Danish Krag I have. I then ran the brass through the 8x58R die. All but one collapsed at the shoulder . Didn't matter if the brass was annealed or not. I then tried R-P 45/70 through the 8x58r and it sized no problem, so the dies work. Any guesses as to why the brass that has been sized to 40/65 gets wrecked ? This is my first attempt to try something like this and I'm stumped. I hate to toss all the brass I turned and start from scratch. Photo L-R:
40/65 case on the left, crushed cases, 45/70 resized to 8x58R.

[craig61a]

I've sized Starline brass down to 8x58r just using a FLS die. I recently tried sizing 577/450 using intermediate dies, and I got crushing. My theory is that the brass below the shoulder is not well enough supported in some the dies. I am looking into using a 40-82, 38-56, and then 8x58r. As for brass Winchester is usually a little harder going by many say.

[EDG]

When you are trying to neck a case that is smaller in diameter than the die interior, the cases bulge out at the shoulder from the force applied. That bulge provides a place for the case to fold and crush.

Once the shoulder is no longer supported you can only size in small increments that do no over load the unsupported case.