I found with mine, a too-light charge (3 drams) put the barrels(right) one above the other by about 2 1/2" at 50 yards, increasing 10 gr. no change, then 20 gr.(100gr.) brought the barrels together at 50 - into the same group. Then another 10gr.(110gr.) made them shoot parallel. Another 10 gr. over that to 120gr., made them diverge and reverse the high shooting, left over right.
I wanted it to shoot well with 120gr. to 130gr., as a heavy game hunter, it would not, so I sold it.
5 shots in the group - discounting the flinch.

I changed from the ticking patch, which was .021" to a 10oz. denim at .0225" and that small change, brought the barrels together at 50 yards.