I have three barrels for my other sigs.

I also have a stash of .357 sig ammo

Is there a conversion barrel or kit to convert 9mm to .357sig.

My other sigs could go down not up. You could not go from 9mm to .357 but you could go from .357 to 9mm.

Has anyone done this conversion?

The modularity of the P320 makes it possible to configure many potential arrangements for caliber and frame size combinations. You did not state whether your P320 is Full Size or Compact, but X-Change kits were/are offered. Availability on Sig's website at present appear very limited, but many vendors on-line offer them, as available.

I have not converted any of my P320s, so can't offer first-hand experience. But, many on this forum have.

I did a quick search for X-Change kits for Full Size and found one, link below. If you have a Compact model, it seems that more options are available.

At one time the price point for the P320 X-Change kits were within striking-distance of the price of a new or used P320, so economics come into play. You will have to decide yourself whether this option makes sense for you.

I have no affiliation with the vendor below. There are a few vendors who are members here, so you may want to reach out to them as well.

Regards,

Doug

https://www.midwayusa.com/product/1020118899

I was hopping for a barrel swap, like I did on my other sigs.

I purchased a Barsto conversion barrel and had it fitted and I was up and running.

With those kit's prices I may as well buy a new gun.

Still hoping someone stops by with other suggestions.

Mine is the P320 Carry

@Merc50 thanks for the link

quote:

Originally posted by sig2392:
I was hopping for a barrel swap, like I did on my other sigs.

I purchased a Barsto conversion barrel and had it fitted and I was up and running.

With those kit's prices I may as well buy a new gun.

Still hoping someone stops by with other suggestions.

Mine is the P320 Carry

@Merc50 thanks for the link

The breech face of the 9mm slide is sized for the 9mm cartridge and is too narrow to accommodate the base of the .40/.357 case. This is one of the reasons why you can go down from .40/.357 but not up.

The closest thing that you can do to reach your objective would be converting to .41 AE. It has the same breech dimensions as the 9mm Para. The good news is that you may be able to use your slide if you bore out the muzzle. The bad news is that the barrel will have to be custom made and the ammo is impossible to find.

You'd be better off just buying a kit or another pistol.

Besides the barrel, the significant issue these days in converting a 9mm P320 to 357 SIG (or 40 S&W) is finding the slide. Barrels for 357 or 40 P320s are larger in diameter than 9mm barrels and their slides are heavier. In addition, the slot in the breech face that the case rim and barrel hood extension fit into is narrower in the 9mm slide and too narrow for the 357 or 40 cartridge. I.e., there’s no way to use a 9mm slide for a conversion to 357 or 40.

I purchased a 9mm to 40 X-Change kit directly from SIG back when they were available and acquired a 357 SIG barrel separately.

I recently purchased a 9mm P320 XCompact and am in the process of using its FCU as the basis for a 357 and 40 Carry model as well as using the XCompact’s shorter grip module with the longer Carry slide. Finding all the parts necessary for that required searching and a WTB ad here for the slide. Springs, magazines, and even the barrel were all from commercial vendors, but I feel very lucky that I was offered a slide through the classified section here.

The 357 Compact/Carry barrel was also something I expected to have to find as an aftermarket item, but to my amazement I got an “available” notice from Midwest Gun Works shortly after I posted the request there.

I know of no way that it would be possible to convert a P365 to 357 SIG. Unlike the parts necessary to convert a 9mm P320 to 357 that are just difficult to find, there are none at all for the P365.

Good luck with your project, but it will involve using more than a conversion barrel. In my opinion the 357 SIG is the best of the big four defensive cartridges for autoloading pistols. Unfortunately, however, not enough other people agreed with me.

With the P320, what you can do is pick up a .40 slide off ebay or some other source, and use that as the host for your .357 barrel, and run that.

You're not going to find a .357 Sig conversion for the P365. It's been made for the 9X19 cartridge, and wasn't built for the .40/.357 Sig.

With a .40 slide, you can run your lower (FCU, grip module) with 9mm mags and a 9mm conversion barrel. Depending on your ammunition, you should opt for a lighter spring (eg, factory spring assembly, or if running a full length, get an aftermrket guide rod that you can run 1911 springs on and tune it for your load.