Rifle Scopes Sighting in Question

Macdaddy

Sergeant
Full Member
Minuteman
Feb 15, 2009
408
52
Clarke County, VA
I have a 100 yard range on my property and am wanting to sight in a rifle for a 200 yard zero. Easy enough, I just have it hitting "X" number of inches high at 100 yards based on the ballistics right? Well maybe, maybe not.

When I use the JBM calculator based on a 100 yard zero, it says it will have dropped 2.3" at 200 yards. OK, just have it hitting 2.3" high at 100 and we're done.

Only fly-in-the ointment is that when I input for a 200 yard zero, the calculator says that the bullet will impact 1.2 inches high at 100 yards. Now I'm confused. Which value should I be using when sighting it in for a 200 yard zero when I'm at a 100 yard range? A 1.2" delta or a 2.3" delta?

The amount is fairly insignificant at those ranges but I'm concerned at 400-600 yards what differences there could be.

I'll of course actually shoot those distances to verify but I want to start off theoretically having it ready to go.

Can some explain to me what I'm not accounting for here?

Thanks