Reality is, 357SIG performance is basically the same as 9mm +P+. Other than maybe a little extra noise from the 357SIG, if you were shooting either out of the 31, you wouldnt know which was which shooting wise. One thing to keep an eye on with the 31 is the underside of the slide where the locking block tends to hit it. My 31 was beating itself to death here, and showed no signs of slowing down, though I was told by a number of people it would. It was peening the slide pretty heavily, and it was deforming the slide enough, that you could easily cut your finger on the sharp edges if you ran your finger across them with just a little pressure. My one 17, which has more +P+ 9mm through it at this point than my 31 had 357SIG, shows only some minor finish wear in the same spot. 357SIG ammo was at one point, the eact same price as .40, when you bought it by the case. I bought a lot of both when it was $250/1000. I sold both off when 357SIG hit close to $600/1000 and .40 wasnt to far behind, back during the last "shortage". Made out quite well too. I know its come back down some, but its still pretty pricey. Even reloading aint all that cheap these days, especially since they use caliber specific bullets that tend to cost a good bit more. You can use some 9mm bullets, if the profile is right, but most arent. 147 grain bullets are closer to the correct profile, but I never had any luck with them accuracy wise. My guns always shot best using Speer 125 grain 357SIG TMJ's over AA #9.