Re: IMR 7828 sc/.300 Win.mag.
Don't worry about IMR having a sensitivity issue. I burned more IMR powder than any other brand and never experienced any. I'm from California and the temperature here varies from the 40's in winter and 100's in the summer. I used 7828 for my 300 Win Mag, 4831 for my 280 Remington, 4350 for my 338 Win Mag, 6MM Remington and 243 Winchester, 4064 for the 308 on some loads, 4895 on my 3030, 3031 on my 35 Remington TC, some 223 and 222 Remington Mag loads.
For the 300 Win Mag, the 7828 is excellent. Never tried the SC yet but I believed the recipe is the same as the original. But just like any powder, they varied from lot to lot so start at the bottom.
Here's my recipe for the 300 Win Mag...
180 grain Barnes TSX
74.5 grain IMR7828 starting load. I never exceeded beyond this load since I'm getting 3000fps already from a 26" barrel, and accuracy is outstanding.
180 grain Sierra SP. Hornady Interlocks, Nosler BT, Speer GS
76 grain IMR7828 Max load
Brass Federal Gold Medal
Primer Federal 215M
To achieve the maximum possible accuracy, all variables must be remove or at least minimize.