I'm using the 142 gr ABLR in mine. But I think any of the AB's in the 130-142 range would work well. I chose this one as some of the game I take isn't the largest deer on the planet. I wanted something that was tougher at the higher velocities inside of 200 yards or so but still held together well enough to punch through an elk at 500 or so.
I haven't tried any of the heavier bullets that are out there but most, if not all, are flat-based, round-nosed bullets. For the ranges over 400/500 yards I'd think you'd want something with a better bc than those heavy one's have. Matrix makes a 150 grain VLD style target bullet but I'd be hesitant to shoot those at any distance where velocity is above about 2800 fps. Same with pretty much any of the 'match' bullets.
Berger's heaviest .264 caliber is 'only' a 140.
I think with any of the Accubonds or similarly bonded bullets in the 140 grain range you should be good to go on any deer-to-elk sized game out to your 650.
