Most load tables list H4198 as a little faster than IMR4198. I have found that lot to lot variation with H4198 can vary significantly. The latest 8 lbs of H4198 required I back off a full grain (33.3 to 32.2) with my 30BR. Never played with IMR4198. Just start at the low end of your load table and work up and you should be fine.
