Jim B.:
I am looking at the data for the last three attempts with the 75 grain Sierras. The highest average velocity is 1,940 fps with 10 grains even of H4227. But the standard deviation was high at 115. As you might expect the group wasn't much. About 5" at 100 yards with the receiver sights.
I thought I had tried H-4198. It was IMR-4198. Twelve grains averaged 1,803 fps. I got 3".
So far, I am getting the best results with Alliant Reloader 7. The last loading yielded me some 2" groups: smaller than 1" at 50 yds. I used 12.0 grains for an average velocity of 1,889 fps. I am going to work up a bit more and see what happens.
The Speer data shows the highest velocities with AA 1680. I have yet to find it anywhere around here. Reloader 7 burns just a bit slower than AA 1680. My dealer always stocks it.
Best load I have come up with so far is 7.0 grains of H4227 behind a Meister 85 grain cast FN. It groups less than an inch at 50 yds. The average velocity is 1,348 fps with a standard deviation of 12. It will be a great small game load. It isn't legal to hunt turkey here with a rifle. If it was, this is what I would pick.
I could shoot it in the barnyard without spooking the horses or upsetting the neighbors. One can of powder will give me 1,000 charges. The 500 cast bullets costs between $18 to $19.
For the jacketed bullets, I think the .25-20 is a bit undersized. A .223 necked to .257 or the .256 Winchester would be better.