IMR 3031 is a good .300 Savage powder. The suggested loads on the IMR powder page work.
I had not heard of Tubal Powder until this post. Cannot comment on it.
A couple of other favorite .300 Savage powders are AA2015BR and IMR4064.
If you have a problem getting cases once fired military 7.62 NATO cases resized with Small Base RCBS dies, and trimmed to length work great.