Gentlemen, I was asked a question yesterday about changing from one brand of brass to another by a fellow shooter and beginner reloader. His question to me was, why the big change in his MOA and/or group size when he switched from new Lapua to new Hornady brass, using the same lots of bullet, primer and powder in his 6.5 Creedmoor and 308 Win? He loaded the Hornady brass the exact smae as he did the Lapua cases. I did not want to give him any wrong info so I thought I'd ask a more knowledgeable community. I understand the difference between case capacity and pressure but I myself don't understand why the change in group size. He is somewhat of a fanatic when it comes to his style of shooting, since its a hunting rifle he waits ten minutes in between shots. He cleans the barrel after every 75 shots and does not use any type of metal brush in the bore. He says it takes 5 shots after cleaning to get his gun to shoot to point of aim on the first cold bore shot. Thanks in advance for your comments