He was close. I believe as close as he was I should have aimed a bit lower. Add in scope and rings, maybe another inch or two lower yet.
Man that sucks. With a gun though it's not much of a difference like with a bow.
With a 100-yard zero the bullet is going to pass the centerline of the scope right around 15 yards. Before that it's going to shoot low, but never lower than the distance between the bore and the center of the scope. So say you have a huge 4-inch difference between the center of the bore to the center of the scope, that bullet will leave the bore climbing and pass the centerline of your scope within about 15 yards for a 12 ga sabot.
For something faster like a 350 legend, it'll cross at about 40 yards. So with a scope sitting 4 inches above bore it should climb about an inch every 10 yards out to 40 yards with a350. In essence, a gun has two zeros, one at 40 and again at 100. For a shotgun it's like 15 and 100.
On a deer-sized target you shouldn't have to hold any different on a deer sized target, even at point blank touching ribs you're only going to be the difference between the scope and barrel.