It's got the same near 13° boattail that the 168 grain Sierra MatchKing does, and that's credited with destabilizing the 168 gr. SMK in the transonic reason. I've had that happen with the SMK at around 700 yards. I don't have any experience with the A-max at that range, though. The different nose shape may affect it. At any rate, if I wanted to go to 1000 yards I'd do what the military did and move to the 175 grain SMK with it's 9° boattail or to the 155 grain Palma SMK or the 155 grain Lapua Scenar.
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member