IMHO Ruger mis-marked (to avoid lawsuits I suppose) those ".44 Specials"... They
should be marked ".44 Long Russian", and the OMV's that are "mis-marked" as ".44 Mangle-Em" oughta be marked ".44 Extra-Long Russiian"!
Now, I can't take responsibility for the actual facts, but when Ruger first brought out the New Vaquero in .45LC, an engineer I met at the Shot Show told me they were proofed to the same level as the OMV's! To manage this, they reduced the index circle diameter (the diameter of an imaginary circle passing through the center of the chambers. This gave the cylinder walls more thickness. What you gave up was the ability to chamber .44-40's as the rims would overlap!
The .44 Russian family has a smaller diameter case, so it will work in the smaller cylinder, and I would suspect gives a bit more wall thickness and pressure tolerance, though I WOULD NOT TRY TO MAKE A .44 Mangle-em (oops) .44 Extra-Long Russian with full-power loads. Besides, you don't need such hot loads for CAS. While I'd admire to have a pair of these .44 Long Russians, my rifle works better in .44 Mangle-Em. So, I reckon I'll stick with my OMV convertibles.