Aaron,
My be it's me, but the recoil impulse is less on my Mountain Gun then my 625 4" JM.
Last weekend I did in fact try all the 4" series I have in my collection which are the two mentioned and also one of my 325 Thunder Ranch models the load was, and is 3.9grs. of Clays on top of a 230gr. lead round nose.
This load is my standard for shooting IDPA matches, I shot 24 rounds through each gun to compare, a bill drill at 21ft., and several target layouts for different scenarios.
My conclusion is the thin barrel Mountain Gun, and also the Thunder Rance, I was able to get back on target faster, verses the heavier 4" JM 625.
For next's years shooting season, I will be using my MG in .45 acp for matches.
Now this perceived recoil impulse works for me in my experience with these 3 that I tried if it works for you, thats yet to be seen, But thats my 2 cents worth.


Joe