When I had my 416RM, I was using Woodleigh 410gr RNSP, still use these in my 416 Rigby, absolutely wonderfull bullet.
I used the Speer too on deer, pretty poor performer in my book.
Powders I used were Varget, RE15 and 748.
Varget was the most accurate with 410gr Woodleigh and 748 was almost the same. 748 was slightly slower than Varget.
RE15 was the fastest, and worst accuracy, but it got above 2500fps.
Unfortunately, IMR powders weren’t available here then, and still aren’t.
Cheers.
