As slide noted, there are (3) mounts. Here is a pic of the rail mount on my 2206. It does cause issues in stripping the slide, and for that reason is a PITA for me, but it is the most functional of the mounts, IMO.

A good 'smith could drill and tap your 422, there is a lot of meat on the muzzle and shouldn't be an issue. These mounts are around $10 on EBAY, I estimate a 'smith would charge $25-$35 to drill and tap. So price wise you are in line with the grip/trigger guard mounts.