JA, Last year I found a post of yours that was at least a couple years old which led me to a process that is very similar. I do not recall where I found that post, but I always wanted to say thanks for it.
I wanted to develop two loads. One for accuracy and one for tactical rifle competition. I did not want to use fully handloaded ammo because I'd end up losing pretty close to 100% of my brass, and Russian ammo is lousy stuff.
So the in between solution was to modify the Russian stuff and make it better.
My accuracy round is still in the works, but my basis is the Silver Bear round with the factory powder measured closely, case trimmed and topped with the same Sierra Pro Hunter .311 at 2.20". I've gotten groups from 5/8 to 3/4" at 50 yards with it in one SKS. I've had that rifle modified since and it no longer shoots that well. Not sure why yet. Going to work on the round itself again during the winter to see if I can bring it back.
The tactical round is a reduced load. I use Golden Tiger as the basis. I replace the powder with IMR 4895, weigh and sort the factory bullets and use only the 123.5 grainers, trim the cases if I feel especially nerdy and seat at 2.197". This round is not as accurate as the Silver Bear but a lot better than factory and with much reduced recoil. It only needs performance out to 100 yards.
Anyway, this is all due to your previous experiments and guidance!