# PX4 barrel question



## Mad Scientist (Feb 20, 2019)

Hello everyone!

I'm trying to confirm something I overheard. Is the outer diameter of the 9mm PX4 barrel, the same as the .40S&W barrel? At Wally-Mart, two guys were talking about how he can simply change the barrel and magazine from a .40 to 9mm and back again, with no issues. This seemed odd, since I thought the 9mm barrel would be a smaller diameter than it's 40S&W cousin. Anyway, thanks for clarifying this for me!


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## denner12 (Oct 14, 2017)

To the best of my knowledge the outer diameters of the barrels are the same. The 9mm barrel is thicker and the .40cal is thinner. The breech face on the .40cal is larger as well


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## denner12 (Oct 14, 2017)

BTW, I own both and while I've never fired the .40cal w/ the 9mm barrel, I have cycled 9mm rounds in the .40cal frame(frames are identical) and slide with the 9mm barrel and they cycle w/o a hitch. The 9mm barrel fits with the same tolerance along with either recoil assembly(which are identical.) The .40cal spring is a little heavier, so, one may consider using the the 9mm recoil spring with lighter loads. Thankfully Beretta uses a heavier recoil spring in the .40 I may add. I really dig my Beretta PX4 compacts.


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