Your Krag's scope is off-set to the Left, so I offer these suggestions:

1. Remove the bolt and sight down the bore with the rifle in a stationary rest. (You can improvise a rest by cutting a couple of "V" notches in opposite ends of a cardboard box). Center the bore on a target at about 50 yards.

Adjust the scope's cross-hairs so they 'aim' about 1&1/2 inch to the left of where the bore is aimed.

2. Do your initial shooting of groups at 50 yards. Aim scope cross-hairs at center of Bull. Tolerate bullets grouping 1 to 1 1/2 inch to the right of the Point of Aim.

At 100 yards, aim cross-hairs at 9 o'clock and shots should be relatively centered on Bull.

By keeping things parallel, with POA slightly and consistantly to the left of Point of Impact, avoids the 'lines' intersecting at an angle and creating greater disparity at longer range.