This will probably come as no surprise, but I thought I would share.
I have a P239 in 357 that is great.
I bought a Sig factory 9mm barrel, recoil spring and magazine.
Fired for function today, and it worked great.
I do need to figure out the sights, but no function issues.

I have a P239 .40 (same as .357) that was "converted" to 9mm usimg Sig OEM 9mm native barrel.

Functions fine with .40 RS and .40 mags. A number of other SF members have found the same. Offhand, don't know if .357 mags will. Give it a try though.

I’ve also done the conversion and successfully use all 4 factory barrels using the .40 recoil spring and .40 mags. The .357 mags will probably work fine for you in 9mm.

I’m not sure what your sight issue may be but FYI, the factory normally uses the same sights (#8 front and rear) for the 9mm and .357.

So, then what's the big deal about having to use a "conversion" barrel? Does this mean that the plain ole 9 mm barrel works in the 40?

quote:

Originally posted by fquico:
So, then what's the big deal about having to use a "conversion" barrel? Does this mean that the plain ole 9 mm barrel works in the 40?

When this topic comes up which is does quite often the key points get left out IMO.
Using the factory 9mm in the 40/357 guns is a looser fit as is the 9mm mag in the 40/357 frame.
I'd consider this for range/fun only and would never rely on it for self-defense use.
Others may see and feel differently though.

This is good to hear - my 9mm factory barrel (threaded - wanted to try it with a can) and a few 9mm mags just arrived.

Note that the 9mm mags will rattle a little in the .40/.357 frame. Slightly wider mag well than a native 9mm frame. Nothing to worry about though.

quote:

Originally posted by fquico:
So, then what's the big deal about having to use a "conversion" barrel? Does this mean that the plain ole 9 mm barrel works in the 40?

First, Sig doesn’t approve of any of this. There IS a difference in the barrel hood between factory 9mm and .40/.357 barrels that could affect the lockup, reliability, accuracy and long term life of the pistol. The breech face of the .40/.357 slide is larger than the 9mm version and therefore the extractor and ejector are not in the ideal position when shooting 9mm through a .40/.357 slide. Using a conversion barrel address some of these issues.

However, using a factory 9mmm barrel has worked for a lot of people who’ve tried it. As well, 9mm seems to function well through both the .40 and .357 magazines (and .357 seems to work fine through the .40 mag but not the other way around). Last but not least, 9mm seems to work ok with the heavier recoil spring of the .40/.357.

I use factory barrels in all 3 calibers and change nothing but the barrel. I use .40 magazines exclusively and most of them have the Sig +1 adaptor originally made for .357 mags installed. I’m approaching 2000 rounds of various 9mm and another 2-3 hundred (combined) of .40 and .357. I’ve shot different brands of both FMJ and HP. I’m using two different factory 9mm barrels, regular and threaded. The pistol has never failed to load, fire and eject. Not once. I would not hesitate to carry my pistol in 9mm.

Having said all that, at least one individual has posted on this forum saying his pistol wasn’t reliable using a factory 9mm barrel. I don’t believe the problem was ever diagnosed or if it was the OP never reported back. Given that, I don’t think its guaranteed any and all .40/.357 P239’s are capable of doing this. However, either the vast majority of the pistols work fine or most of the people that have issues aren’t posting about it.