I've found a couple published loads. Both show 8.8 gr. max load using 115 gr. JHP.
I substituted a 115 CPRN and starting at 8.3 gr. worked up .1 gr at a time to 8.7 gr. So far nothing has cycled the test pistols. At 8.7 gr. the slide will occasionally stove pipe empty brass but not often. Going to try 8.8 gr. next but I doubt the additional .1 gr. will make this a winner.
At 8.6 & 8.7 accuracy was good, better than my standard 4.3 gr TiteGroup with 115 CPRN. As can be imagined 8.7 gr. is a very quiet load too.
Anyone have experience using 4227 in a 9mm?