I'm developing loads for a new Remington 300 Win Mag and have tested Reloder 22 and IMR4350 so far. I picked up some H1000 to trial next. For bullets, I've tried Speer 180gr SP, Berger 190gr Hunting VLD and Berger 210gr Hunting VLD bullets. All seem to be capable of 1/2MOA accuracy. I did some brief chrono work and had very favorable results. My questions to the group is primer choice. I've received conflicting views on Magnum versus Large Rifle primers for this cartridge. My loads so far have been with Winchester Large Magnum primers. I did slip in a couple rounds with Winchester Large Rifle primers to compare velocities across the chrono. These Large Primer rounds gained about 35fps over the same loads with mag primers. At the recommendation of a local gun dealer and avid magnum shooter, I picked up some Federal 215 primers to trial. Recommendations?