Wow. 100% the RMR FMJs are the issue. The Hornady 55 soft points did so much better.
Different range today, benches are old warped plywood affairs without height adjustments on the seats, so a fair bit less accommodating (but vets shoot free here, $25/day at the other place, which was the only open local for months). So I rested on the mag, using a yoga block under the baseplate. I shot at 40ish yards, since they had 36 marked and it was close to what I *should* have dialed in as near zero. My elevation was actually on for most of what I ran today.
I tried TAC with the Hornady rounds, just three weights to start, 25, 25.3, 25.6. Using a tape and not calipers, it went 15/16", 7/8", 13/16", so I may keep increasing charge weights further to see if it tightens up more.
I then tried the same bullets with H335, only 25 & 25.3 grains. 5/8" at 25, 1/2" at 25.3. I had read over and over online that 25.3 under 55 gr bullets was an accurate combo, and that seems to bear out. Considering the suboptimal shooting position, I can't complain.
I did one 3 rd group of the RMR FMJ with 25 gr of H335. Two inches and eleven sixteenths...