I am getting ready to start reloading 357 Magnum for two Winchester (Miroku) rifles, an 1873 and an 1892 both with 24" barrels. I am a target shooter (so I want velocity but will certainly begin with starting recommendations). The two powders that I am most interested in are IMR or H4227 (apparently same thing now) and Winchester 296. Starting out I will use them with Hornady XTP 140 or 158 gr bullets. Both are listed in Hornady and Richard Lee's reloading guides. I am attracted to these because they are high volume (less likely I will double fill a case) and slower burning (better for longer barrel) powders. I would appreciate comments on is one better than the other; if so why. Or is there a better powder than the two I am considering; again, if so why.
Secondly, primers. The guides say small pistol but I have read a few people saying they use small pistol magnum primers. One commenting that slower powders are better ignited with magnums. Would appreciate the experience of this group.
Thanks & Regards, JimB