When you resize your brass without the expander ball in place, what is the O.D. of your neck? I have a Hornady FL die which seems to make them considerably smaller than necessary.

My 204 Ruger brass (Winchester) comes out @ .217" using RCBS dies.

Yeah, .217 is about where mine comes out. This seems pretty tight since the diameter after passing over the expander ball is about .223" with brass thinned appropriately for my tight-necked chamber (.20 Vartarg). An unexpanded diameter of about .220" would seem to be plenty tight and would work the brass less.

Stone,

How tight is the chamber neck, on this new 20VT of yours?

A pic wouldn't hurt, either.

Kevin

Kevin, the necks of the fired brass come out of the gun around .230". I'm thinning the necks so that the loaded round is about .002" smaller.

.217" seems like it is mashing the brass somewhat smaller than needed, then expanding it back to the proper I.D. But maybe .217" is about what all of the die makers use.

To avoid overworking my case necks I've jerry-rigged a Lee Collet die using .204 Ruger parts. I can only size the upper one-half of the shorter .20 VT necks, but this seems sufficient to provide enough bullet tension for the very low-moment bullets of a .20 cal. No lube to mess with, either.

It is a little easier for me as I use Wilson neck die with a .226 and 228 bushes. Have a .228 loaded neck dia and a fired neck dia of .230 from a .232 chamber neck.
I have necked 221 brass and reformed 222 and 223 brass. I had my Hornady die opened up in the neck to overcome the same problem you have. Opened to .226 should be fine

I had thought about opening the neck of my die up -- but I couldn't find a drill bit in my set which was quite the right diameter

Seriously, who can you find that can do such precision work on such a very hard metal, and is it affordable? I wouldn't think that most machine shops would accept such a small order, or at least that their minimum would be way more than ordering a custom die.