I have a dozen or so new Ruger Mark III 22/45 magazines. Will they fit in a Mark IV 22/45, or should I find an older version of the pistol? I'd like the new version with the cool stuff on it, but mags can be spendy and I prefer to shoot at the range, rather than load mags.

I do not own a MKIII or MKIV but a quick search of the Ruger Forum website postings say the metal mag bodies are interchangeable between the two specific 22/45s BUT you have to change the plastic base plate on the MKIII magazine for it to function properly in the MKIV. Baseplates are available directly from Ruger.

Thanks!