Years ago it was always suggested to use magnum primer's when using spherical powders. Seem's those powder's have a coating that is a bit hard to ignite. Well I've never used a lot of that type powder so when I found a keg of H414 a while back, I just used my standard primers. They didn't work to bad but I was using 70gr SMK's in my 243 and considering the bullet didn't like what I was getting. Looked thru my primes cabnit and found one bow of Fed 215's, there was 15 left in it. Reloaded the two best loads I'd found with my favorite Herter primer's and the same loads with the Fed 215's. Well the 215's cut the group's in half. Now instead of pretty nice group's. the bullet's hole's touch.
That spherical powder sure does meter nice too. Now that I have so much, I'm gonna find other use's for it.