cast boolits and tight chambers

[30hrrtt]

I just cast some RCBS 32 170 FN for my model 94 Winchester in 32 Special. I put an unsized one in a case just to see how it would chamber and it was tight, having to use a little pressure to close. I thought it was the nose ride section but it was the end of the case, (marks around it showed some compression), so I started doing some measuring.

Fired case necks in this gun are .344.
With jacketed rounds the neck dimension is .341, leaving 3 thousands for expansion, (my Browning A-bolt 30-06 is 6-7 thousands over).

The bore slugs at .322 so I sized the boolits to .323.

With a .323 boolit in the case the neck is .343 and a hair. That leaves less than a thousandth for case neck expansion. When using jacketed bullets, I try to have 2 to 3 thousands expansion. I found in my Herrett and 30-30AI and jacketed bullets that without room to expand, I get pressure spikes and accuracy drops. I'm thinking if a case is a little thicker it may even be snug even if it will chamber without forcing.

Will this be alright with cast as they are softer than jacketed or will I run into pressure problems with such a close fit? I know I could size down to .321 but am hoping the one thousand over bore slug will work. If it is tight, the other option would be to neck turn but sure don't want to think of that.

[runfiverun]

thinner brass.
measure the thickness on some win/rem/fed brass.
some is 13 thick some is 12 thick.
that would get you what you want.

[303Guy]

Not sure this will help but I often encounter a cast boolit (paper patched, actually) seated into an unsized neck that results in stiff chambering. Since I am deliberately keeping pressures low, I cannot say I have found the 'tight chamber' to be a problem. I sure as heck would not like to try a 'full pressure' load under those conditions without working up. (My chambers are not tight - I just load somewhat large boolits with the idea of swaging them in the bore).