Dave,

Been doing 45 Supers in a S&W 625 PC for about a year now. Should be about the same as your JM, as the guns are pretty similar. The biggest difference between yours and mine is the rifling. Mine is broach cut and supposedly the JM is more polygonal. I have seen a ton of posts on the S&W forum where reviews are mixed about the accuracy with the JM and lead. I do know mine shoots straight lead, wonderfully.

As to 250's at 1100, that is about my limit, that I have imposed on mine. But, you may have a problem with the bullets in the unfired chambers, staying in the case. I have two solutions. I roll crimp, and I use 45 Autorim, which is also roll crimped. I note this as if desiring to have the exact same ammo for both the revolver and auto may be a challenge, as a roll crimp is obviously a no go in the Glock. Obviously this is something that you would have to experiment with. I can get to roughly a 250 at 1000 before I start to see some bullet creep, with a taper crimp (same ammo used in my 1911).

You probably have found that many folks refer to having had or know that Clark Custom will chmaber the 625's for the 460 Rowland, a 40K psi round. I have a lot of experience with the Rowland, but still am not comfortable with my 625 at 40K. I run my Supers at what should be in the neighborhood of 28-30K, but if doing so, you are going to be hard pressed to find a lot of information on long term results of doing so. I have not read any detailed experiences of the Rowland in the 625's, from guys actually doing it.

I am very pleased that my gun will function with acp's with and without moon clips, as well as the 45 Autorim which does work perfectly well as a Super or standard loading. Some of the newer 625's have been reported to not headspace correctly, without clips.

I shoot Rowlands and full blown supers out of 1911's, and am trying very hard to be good, and not purchase a 41 MOS. One of my 1911 slides wears a low cut JPoint, but you guys with Glocks seem to have a better platform for pressure, than the 1911. If you are holding your 250's to 1100 fps, then you are certainly not mis-behaving ;^)

Craig