Winchester Highwall 40-70 SS Chambering Problem

[bryany]

It will stretch a little, but may need to still be stretched. But unless you're shooting patched bullets I don't think the little bit the case will be short to be a problem.
Buffalo Arms sells 30-40 brass formed to 40-70.

Most of the 40-70 SS brass I have used required sizing of the bottom quarter of the case smaller than the FL die could do. I cut down a FL die so I could run the case all the way to the rim. That made them chamber just fine. Subsequent loadings have not needed this step.

I cut the bottom 1/8-1/4 inch off and then cut most of the top half off. A good machinist could probably make a sizing die but it was easier for me to ruin a FL die.

Bryan