As you mentioned, you might experiment with seating depth, but I use 2.26" or just a hair under. Best AR load I've found with the Hdy. 75 Match HP has been 24 H4895 and CCI400 primer. CCi450 or Rem. 7 1/2 would also be worth trying. This is an accurate load, but the accuracy has always been slightly behind that of the Sierra 69 MK or 65 GK to 200 yards, about as far as I shoot any AR.
I've also tried TAC powder with the 75 Hdy., but I've found H4895 slightly superior for accuracy.