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I'm guessing you arent cleaning the residue of lube and powder from the previous brand of ammo before going to a "new"? Yeah, that's normal.
No, I'm not cleaning anything. I was doing group tests and switching ammo brands to see the effect. It's a heavy stainless target barrel and I've found it's not a good idea to scrub the barrel more than about every 3,000 rounds or so. After a thorough cleaning it takes quite a while to foul and group well, then it's no better than before the cleaning. I talked to a couple of guys at the range that are into the highly modified 10-22's and they convinced me that cleaning stainless target barrels is not really a good thing. After a lot of tests, I'm convinced they are right.
My point was, don't mix ammo types if you want good groups, use up one brand, then make a clean break to the new batch, and expect your groups to open up for 20 or 30 rounds before they "settle back in", and it may not be to the same point you were sighted in at before you switched.
Trying one box of new ammo and deciding it's not grouping well may not be a legitimate test, from my personal experience. Looks like Perferator has seen the same thing when switching brands.