Speer #13 reloading manual suggested a magnum primer for use with ball powders..... my loads using H414 in my .270 got more consistant in cold weather when I switched to the magnum primers......
In my experience, v-N340 pistol powder is sensitive to heat- loads developed in march were fine - functioned just fine, cases looked normal..... but when I shot them at a pin match on a hot July afternoon, I had several FTE, headstamps battered, primers flat, with a ridge around the pin dent....