My Dad had .300 Savages around for a long time and of three when he gave us boys his rifles, I selected the bolt action Remington 722 because I feel out of the bunch it was the best to reload for. The others were a Model 81, and a M99. I rather doubt the barrel steel in my Model 722 is any different then in the 6mm Remington, 257 Roberts, .222 Remington, and the .308 manufacture in the same period by Remington.
I have had good results with AA2015, IMR4320, and IMR4064. My hunting loads are based on near maximum loads from three generations of Hornady Manual, including the most current. In addition I have check data in other manuals. I have settled on IMR4064.
The velocity from the 24-inch barrel gives the .308 a run for its money when the .308 is fired from a 22-inch barrel. The fact is that when it comes to barrel length the extra two inches count.
Going backward a lot of years a brother was deadly on deer with a Savage M99, 300 Savage, with a 20-inch barrel. The same brother recently acquired a Remington 760 in .300 Savage and plans on loading recommended loads using 150-grain bullets with IMR4895 or H4895.
I have spent a lot of time developing my .300 Savage hunting loads, but I would not recommend that my brother start out with them. He is an experience loader who will systematically develop a load(s). He has been loading for over 40-years and has used a far greater selection of powders then I have.
There is a big bunch of powders that fall in and around the IMR4895, and IMR4064 burning rate. They have targeted these powders because they fit a need, and there is a market for them. The question is are they any better? I rather doubt that the industry is spending money on .300 Savage load development.
A quote from Speer Manual #12. “We found that two newer propellants, Reloader 15 and VihtaVuori N140 allow up to 100 feet/sec velocity gains with heavier bullets compared to other powders.”