If you mean short-stroking, it's likely because the burn rate of H322 is too fast for the application. A slower-burning powder might solve your issues.
AR-Comp has been the most accurate in the dozen or so barrels (and powders) that I've used. Velocity is respectable, but not the best.
This might seem odd, but my perception is that AR-C's burn rate is slower than 8208, but in the Grendel case, its max charge is slightly less than 8208. A weapon is less likely to short-stroke with AR-C, and recoil is drawn out into more of a push. 8208 seems to have somewhat of a fine line between safe and excessively hot loads.
Using 123gr bullets, 27.7gr of AR-C or 8208 often works very well. AR-C will usually be more accurate, and 8208 will yield slightly more speed.
CFE-223 (and Leverevolution) is the velocity king in the Grendel, but at the expense of temp sensitivity. With max loads, it's unmistakably harder on the weapon if tuned for other powders. Burn rate is quite slow compared to AR-C and 8208. (Uses ~3+ grains more powder.)
AR-Comp has also been very accurate for me in 223 with 69gr bullets, and in 260 with 123gr.
Examples of AR-Comp (w/ 123gr) that I have pics of include 5- and 10-shot groups at 100 yards using a Satern barrel:
And here's the Satern-tailored load used in a Shilen:
To put my experience in perspective, I'm probably approaching ~10k rounds total of Grendel fired (nearly 6k in one barrel), have used ~1 dozen barrels, and have burned ~25 lbs of AR-Comp.
