I am no expert, but I do agree with the experts, like 500nitro, exaust every option before changing anything made of steel! First off, I would wait till I could get a better day for shooting. Then start with fouled barrels, but cool barrels. Fire a four shot group with the right barrel, when the rifle is cool again, then fire a four shot group with the left barrel, at two different targets. The barrel that fires the worse inndividual group, is going to be about the best composite group you can expect, with both barrels, with that load. Then fire the cool rifle rt, lft, rt, lft, for four shot composite groups. This is the order the regulators at the maker's fire for the regulation when being built, and some times makes a lot of difference. You did not say if the barrels are shooting wide, or crossing. If they are shooting wide, and high, which is what I suspect, they need speeding up a little to get less barrel time! This is likely to bring the barrels into a tighter group, and lower. The change in primer may just do the trick, but I think you need a little more powder!

Then sometimes a double will simply not follow the rules. Who knows why?

I also agree with 500, about the CCI primers, I use nothing else, and have had zero problem with them. A couple times I've had to use other primers, and my load with only the primer change, did not regulate!