are you doing a better job of 'benching' that rifle when you get upset? are you holding it tighter into the pocket of your shoulder and handling it better? are you closing up the action with more gumption which may help with the accuracy?
i'd suggest you go with a milder primer with a relatively-fast, single-based propellant like imr-4895, and work up to a heavier load. that heavier load will give you a greater load density which may help with accuracy. you aren't getting two groups laid out like a poor ignition problem with your load. if there was ''vertical stringing'' i wouldn't suggest the milder primer. why not try a winchester small rifle primer?
i get great results in the .223 with the 7 1/2br remingtons shooting double-based, slower powders.
good luck,
ss'