Originally Posted by GRR
No, a 357 sig barrel won't fit in a 9mm slide. Bigger diameter. Breach face on the 9mm is too narrow also. A top end swap would be necessary. I'd probably change out the 9mm ejector for a 40 cal also. You can put a 357 sig barrel in a 40 cal Glock.
Also, a 9mm conversion barrel will fit a .40/.357Sig slide.