I believe the US Army used a 300 yard zero, which puts the bullet a bit higher at 100. With a 300 yard zero and a a true CoM or stomach hold, this will take you out to 350 yards with no sight adjustments for a man sized targets. For all intents, basically from muzzle to as far as you can spot a target in cover (and then some). Assuming you only have a partial target due to cover/concealment, a handy feature of a 300 yd zero with with M1 ball ammo, is that from about 100-200 the bullet will be about 5"-6" high. At those distances it's very difficult to aim directly at an enemy solider trying to use cover and not have the front sight blade obscure too much of the target for an real accuracy. Putting the blade directly at the base of where the enemies body meets the ground will pretty much ensure the round will impact the enemy due to the 4"-5" rise in terms of impact versus line of aim. Ideally you'd hold low, so that worst case if you're round hits a little low, the round has a good chance to skip into the enemy, or at least throw debris. Debris being kicked up by close range bullet strikes cause far more/better suppression then rounds cracking past overhead. With the first you know the round was aimed at YOU, and was close. With the second it could have simply been a random round that had nothing to do with you.
Intelligent selection of a zero for a rifle, can dramatically increase the effectiveness of the platform in a combat environment.
-Jenrick
