Re: Different brass same primer and load
i have had done a water capacity test with different .308 cases. didn't do lapua, but did federal, winchester, and hornady-match. federal had the smallest capacity, winchester and hornady-match were bigger. winchester brass is supposedly prized by the LR guys because of this because you can jam more powder in.
in practice, FC brass gives me higher velocity with the same charge compared to winchester and hornady brass. winchester and hornady give the same results - not too surprising since they seem to hold within a few percent of the same water capacity.