Tim: IMR 4350 would think FPS 2550 low side 20 thousands off the land.
I ran out of CCI large rifle primers and a friend gave me a box of winchester primers I never in the last 35 years of reloading seen a box of primers that stated
LARGE RILE AND MAG RIFLE PRIMES:THERE ARE NO NUMBERS LIKE NO#8 OR #8 1/2
I REALLY DON'T KNOW IF THEY ARE MAG: PRIMER WHICH THE BOX SAY OR LARGE RIFLE???
BUT THEY WORK