I have a blue Model 77, Mark II in 7 Rem Mag. When I 1rst started loading for it, I used CCIs, got several misfires from them and only from them. I have had issues with CCI primers in other calibers, too. I prefer Winchester primers, but some folks swear by Federal. Winchester primers are definately preferable for hard to ignite ball powders. Ball powders were initially developed by Olin. Olin formulated their Winchester primers for their powder. Heavy loads in big cases also require highly reliable, consistently hot ignition.