My chronograph says that my rifle shoots AE M855 at an average muzzle velocity of 2928fps out a 16in barrel.

50yd zero with 2.5in sight over bore keeps the bullet path within about an inch and a half of line of sight out to 230yds then about three inches below line of sight at 250yds.

100yd zero keeps the bullet path within about an inch and a half of line of sight out to 180yds then about six inches below line of sight at 250yds.

I live in the woods of Tennessee where shooting other than at the range isn't likely to be further than 250yds unless firing down the highway . I shoot offhand and use a 1x red dot for point and click center mass shooting.

So..... while some may quibble that a 100yd zero has a flatter bullet path at intermediate distances or that it's further below line of sight from intermediate distances to 250yds than a 50yd zero, either would serve my expectations of the rifle, ammo, sighting system, terrain and my abilities for the intended use of the rifle. That said, I use a 50yd zero.