According to Ray M. Smith's "The Story of Pope's Barrels", Pope bored the Krag .22 short barrels eccentric at the breech, approximately 7/64" off center. This would be about .110"
The rim diameter of the .30-40 Krag case is .545" and that of the .22 short is .278". The respective base diameters are .457" and .226". The distance from the edge of the rim to the base of the Krag case would be .044" and the same dimension with the .22 short cartridge would be .026", which would be the amount of room the Krag extractor had to engage.
The difference in base diameters is .231", divided by 2 would be .116", only slightly more than the amount of the off-set, so that, assuming the off-set was vertical and that the Krag extractor gripped the Krag rim all the way to the case body, the Krag extractor should engage with the .22 short rim with no difficulty.
