What would cause a bullet to rise going from 50 to 100yards?

[Jpron]

My son is trying federal bor lok out of his cva optima. It shoots about 1.5 inch groups with hornady sst 250 gr. We might be going to Colorado this fall and thought we'd try the Federal's. He's getting about a 2 inch group at 50 yards . When going out to 100 they are rising another 4 inches higher than where there hitting at 50. We're using black horn 209 at 110 gr. Any ideas? And no it's not him.

 

[HARPERC]

Is it scoped? The easiest answer is line of sight vs line of bore. Google it for pictures. It seems a bit much with iron sights, and I don't know muzzle loaders. Second guess is he's got a different sight picture at 100, and holding a little more front sight at a 100.

 

[Jpron]

Yes on the scope, I was going to use the scope to get the grouping, then adjust open sights to the group

 

[lancetkenyon]

Bullet is crossing line of sight over bore and continuing it's path before gravity has pulled it down past the line of sight again.

 

[Hand Skills]