It's an interesting question. More pressure but less power (the 40 will launch a bullet 10 grs heavier nearly 50 fps faster).yes but my concern would be. is the frame strong enough to take the .357 pounding. day in and day out ?
I am just not sure but I don't figure the .357 barrel will wreck a .40.
I have not fired enough rounds out of my regular 9mm P-35 Converted to .356 TSW enough to tell whether it will camage the gun or not. I is however a bit more intense than the .357 Sig round ( most of my ammo is Cor-Bon which drives a 124 at 1500 fps).
Good luck with the project Wes!!!