I have a set of neck size only dies for 7/08, I also have 100 virgin brass. If I test say 30 of these with varmint loads and then mix them with the other seventy that are FL sized Virgin brass, what difference can I expect in pressure & P.O.I if any?

No telling, but would not be conducive of the best accuracy. Once they are fire formed in the same chamber and neck sized they should be OK.

You can expect no difference in pressure. It would be unusual to experience a difference in point of impact. You MAY experience a difference in group size (although the group centers will likely remain the same), but ironically, depending on you loading methods, die fit, chamber fit, and a number of other variables, your groups could be better with the "virgin" cases than with the once-fired and neck-sized cases.

I say "virgin" cases, but actually, you're going to have had to run them through your sizing die to iron out the uneveness in necks, and if you follow my practice, you'll probably also chamfer the insides of the necks, so the cases are unfired, but hardly "virgin".

I always EXPECT to have my best accuracy results with the once-fired cases, but this is not ALWAYS the case.

quote:

Originally posted by Rambo:
what difference can I expect in pressure & P.O.I if any?

As already said, probably bugger all, but why
"mix" them, shoot them first, or last and then
you tell us what happened.
On my last test shoot, my worst group just happened to be one where I also had some FLS ones as well. They shot as badly, but into the
same group. Now there is consistancy for you.
:-) JL