The problem with Berdan cases is re-priming them. You won't find berdan primers on the market and even if you did, they don't use standard sizes like boxer. So a .303 case from one manufacturer may have different size primer than another. And neither of those may be the size of a standard boxer type large rifle primer. So even if you popped out the primer and drilled out the anvil to make a center hole for a boxer primer, that primer may not fit.
That is (sadly) the case with all the GP11 ammo on the market lately. Kills me to throw away the brass but the primer pockets are too big for standard primers.
I have converted some 9mm largo pistol cases from berdan to boxer, but I have never had luck with larger cartridges.