Well, I've been off the forum for a while (had to go back to school) and I'm realizing how late I am on here, but I can at least contribute this: The 123gn Hornady AMax does fantastic in my JP (22" 1:8) barreled Grendel (Grendelyn, to me...). I expect 0.5" with this, and have shot several 0.3" (5 shot) groups with these rounds (no wind and good form days of course, lol!). I've matched that with the same bullet over 26.5gn Benchmark, Fed match primers, and my ability to shoot well enough to tell which round is better (or if there is a better load) just aint there.
FWIW, the handloads are using neck-turned, junky hornady brass, shoulder bumped and then neck sized.
Here are the 1st 3 shots I sent when I barreled up:
FWIW, the handloads are using neck-turned, junky hornady brass, shoulder bumped and then neck sized.
Here are the 1st 3 shots I sent when I barreled up:

