My accuracy load for a 99 in 308 is 44.0 grains of IMR 4064 with a 150 grain bullet. In an 99 E with 22" barrel, that gave me about 2,575 fps with a Nosler Partition bullet. In my current 99 E, also with 22" barrel and the Hornady 150 grain Spire Point, I get 2,625 fps. So I'm basically duplicating 300 Savage velocities. I worked up that load 30 years ago in a friend's rifle, and it wouldn't take high pressures. I think the chamber was rough. My rifle isn't as fussy, but that load shoots so well that I use it. I also tried 40 grains of IMR 4895 for about 2,250 fps. Accuracy was very good, pressure even milder.
The beauty of the 308 is pretty much any mid-burn rate powder works well. Varget, any of the 4895s, WW-748, AA-2520, any of the 4064s, and other can be substituted for my choice of IMR 4064.
