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Been doing more load development and studying. I have a few things to offer.
3031 is the powder of choice for 25 Rem, in all bullets. It has a near ideal comibination of speed and density that make it suited to the lower pressures the older guns operate at. I have tried 14 powders and none beat it.
There is a sweet spot for the 117gr bullet at 2300fps that can be had with 25.5gr 3031, give or take 0.5 grain. Pressures are mild at about 30,000psi. This load shoots as good as my eyes can see in the 30 express with peep sights (2 inch groups or less), which is plenty good for field use. Approach 26.5gr and expect the groups to fall apart as you get near a point where the shock wave is at the muzzle as the bullet exits.
There is another sweet spot just under 2500fps, but that requires 28.5gr 3031 and runs 40,000psi, which is getting a bit high for the 8 and 14.
I would advise against 4895 (H or IMR) in the 25. 4895 is normally a very versatile powder, but it is unstable in the 25. Just a quirk of how the barrel harmonics line up with the burning speed. Velocities are erratic. I also got some nasty (hard and rough) fouling about 1/3 of the way forward of the chamber. Once that fouling builds up, the groups go crazy. It appears that there is a secondary explosion occurring at that point in the barrel. This happened in both my guns.
tbury noted that his accuracy went down as his gun got hot. I think what is going on is that as the barrel heats up, the velocity goes up enough to push the velocity out of the sweet spot. 26gr ran 2345 after my barrel got hot. The sweet spot abruptly ends at about 2325fps.
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