Building "regulating handloads" and "building a set of regulating barrels" are different things.

Creating a set of "regulating handloads" is basically assuming the double rifle barrels are already regulated. The handloader is trying to match or find the bullet weight, powder weight, velocity etc that duplicates the original factory load used OR magically achieves the same results.

Regulating barrels is the process of test shooting and changing the wedges between the barrels until the right angles are achieved to shot parallel or meet at a given distance. A particular factory or handload is used as part of this process.

There are a number of gunsmiths and amateurs here on NE who have done this and do this. One of our moderators even says it is not that difficult ... for him and other talented persons maybe.

But if you have an adjustable barrel double rifle, it is a form of regulation still to make the manual adjustments to get it shooting properly. Same principles but far less difficulty.

Regulation of shotguns is of course FAR EASIER as the same precision is not required.