When changing gen2 G17 to .357sig which barrel is correct please? — 4 Answers

Cannot be done. That’s why you buy the .40 S&W(G22)or .357 Sig(G31)and then buy a 9mm conversion barrel since the slides hole the barrel protrudes fron requires a larger diameter hole than your G17 has which is why the aforementioned lather caliber pistol must be bought first since they then can make the 9mm thinner in diameter barrel than your G17 just a little fatter in diameter to fit the bigger diameter hole in the slide. So what I’m saying is always buy a G22 or G31 and then you can run at least three calibers out of one pistol using correct barrel and mags. 9mm, .40 S&W, and .357 Sig all from the same gun and slide and only might have to swap extractors for proper ejection but that’s cheap and easily done in the field if you have enough skills to put a round peg in a round hole.

It fits all generations, but you will need the Glock 31 slide because the .357 barrel has a larger O.D. than the 9mm.

You will also need to replace the ejector in the trigger housing to accommodate the .357 sig round.