I'm taking out the MK12 tomorrow, I have about 9 different boxes of ammo including the mk262 and various cheaper rounds. I want to test the accuracy, to see what the groups look like. I'm going to have a bit of fun with it. 3, 5, and 9 shot groups to see how they act with different temperatures of the barrel. When I transition to the next type of ammo is there anything I need to do to keep the playing field level? I have watched a few reviews online usually its a 3 shot group then let the barrel cool down, some people do bore cleaner and then enough patches until it comes out clean before moving to the next ammo. I'm still new to this long-range stuff as I'm sure I've said countless times. If I do that I have an otis cleaning kit should I run a brass brush down it a few times as well or whatever their brushes are made of or just stick to the patches? I just want this to be the most level playing field possible. I'm honestly just going to have fun, but figured why not. I'll eventually do the same with my 308 once I get accustomed to it. What do you guys recommend? I had a guy in the army with me that worked for daniel defense for a bit, and he used to harp on not cleaning m4 barrels until you see accuracy degrade something about filling imperfections in the barrel. Anyways any advice much appreciated. Actually one more thing. I hear if you're doing this whatever ammo gives you the best group you should adjust your zero/zero stops to. If I ever want to let someone else shoot my gun (girlfriend) but don't want them to shoot my expensive shit can I have a zero for the cheaper shit?