Handloader magazine did a test on new/old/mixed brass using a 45 acp from ransom rest. Would take some time to actually find it. If memory holds, same head stamp made a difference. As did new vs old brass. A lot would depend on your pistol,brass, range capability etc.

example-Your pistol/load is capable of 1 in accuracy, but us mere mortals are only capable of 4 inch accuracy with the 1 inch accurate pistol. Then how accurate are we at the same distance with a pistol/load that is capable of 2 inch accuracy?