I had a .58 Kodiak once. With 85gr. 2F GOEX the barrels crossed by 2" at 50 yards along with the right barrel shooting 2 1/2" lower than the left barrel.

At 100gr. of the same powder, the barrels shot one on top of the other at 50yards.

With 110gr. of powder, the barrels shot parallel, shooting 2 overlapping groups with their centres exactly bore axis apart.

With 120gr. of the powder, the barrels reversed what they did with 85gr. of the powder, being that the barrel crossed with the right barrel shooting exactly 2 1/2" lower than the left barrel, as well as 2" to the left.

This just shows that 'they' need to be tested with a variety of loads.

The .562" pure lead ball with .0215" ticking patching, shot identically to a .574" pure lead ball with the same patching & powder charges. I did not find my hold changed anything as to point of impact.
I rather had fun with the successive right the left rapid fire hits on the steel gongs on our trail walk.