dylan's thread has just too many vaiables to determine if its only the brass. To begin with the two different brass are being shot out of two different rifles by tow shooters. No mention to the fact that both rifles shot both types of brass. So you have different chamber dimensions - no matter how slight - which can cause different pressures. Yes, both loadings came out of the same dies. But that is only one constant as is the charge and other components. Besides like Secondchance stated you are only talking 1/8" difference in group size. At 100 yds this variance is insignificant.