I think you will generally find that accuracy is the best with the proper primer for the case capacity of the caliber. I use Remington 9 1/2's (coldest primer) for small calibers like .22-250 and .243, Winchester and Federal standard primers for medium cases, and Federal 215's for calibers that hold more than 80 grains of powder. There are exceptions, though. Only problem with using a "cooler" primer with a large capacity case is that, even though it may turn in a good group on a warm day, cold weather ignition could be an issue at a most inopportune time.