I use mag primers on all spherical (ball) powders, personally.
If you're looking to burn up the H414 I see no reason not to; it's got a burn rate near identical to 4350s which shine in that cartridge so it should work well.
I've always had best results from high load densities with H414, and while it is said to be pretty temp sensitive so is IMR-4350 which I've run in the Better Bob (AI) under 100s in 90 degree weather down to -10 and not experienced shift in POI out to 250 yds. Of course past performance is not indicative of future results yada yada yada.
Good luck; great cartridge!
