Does anyone have any experience with these powders? I am new to large overbored magnum powder hogs and new some insight. I could right a book on Medium and fast powders, but know nothing of these super slow powders. I am loading for a 300 WBY mag. Planning on using a 190-200 BTSP. I heard that RL22 is the same powder as Norma MRP which I would assume is what Norma uses in making factory Weatherby ammo. Is RL25 a Norma powder also? I shot a few(60) rounds of 300 WBY that was loaded with H1000, but that is my experience with it. IMR7828, I know nothing about. Concerns with these powders would be the effect of temperature on velocity and group size.