IMHO you will not get good information on your reloads till you have fireformed your cases, some case's will need more stretching or filling out than others so there can be a big difference in volume
as far as how many shots to be able to asses a good or bad group when testing, that's up to you
I usually test with 3 shot round robin groups then verify good groups with a 5 shot or 10 shot group,
but understand this that if your first and second shot are 2-3 inches apart there is no benefit in shooting again, is there so why would you keep going to 5 shots
once you have found your sweet spot you should be able to still get a good group with a bit of variance in reloads
I would suggest you fireform your cases and then do your testing using an ocw test
http://optimalchargeweight.embarqspace.com/understand though that there are other things that can make your .5 group different than internal volume
hope it all works out for you
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