Breach face will be different, barrel outer diameter may be different.

If the barrel OD is the same then it will work, but it will be headspacing off the extractor vs the case mouth

 

Take a look at this sigtalk thread regarding a 9 barrel in a 40 slide, starting at post #14.

https://sigtalk.com/p250-p320-p320-x-5-pistols/391028-p320-caliber-exchange-kit-discontinued.html

 

The muzzle end of the 9 mm slide is too small for a 40 barrel. The hole in the 40 slide is too big for 9 mm barrel. The later will function but the accuracy suffers, in my opinion. I’ve personally tested this scenario. Maybe a thicker 9mm barrel would work? I heard X5 barrels are thicker. You need micrometer readings, not pictures.

Ian


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This is what a .40 to 9mm conversion barrel is:

The outside diameter and lockup (rear) areas are bigger matching the .40 dimensions with the inside chamber and bore diameter of a 9mm pistol barrel.

This ONLY works if you have the larger diameter slide to work with. (You do)

Just buy a Bar-Sto conversion barrel. Its like $300 ISH, but is designed and made for this purpose.

Only issue is extraction. Brass usually ejects fine, but not with as much force due to the diameter differences. .40 versus .356 (I don't recall exact rim measurements) but you get the idea hopefully.

 

Thanks that info help me so much! I assume that the outside dimensions of this type of conversion barrels match the original so you would not have to make changes to the spring either right?

 

Thanks I will look at it

 

By the way.

I received a SIG factory sealed SIG P320 caliber exchange kit to convert a compact from 9 to 40 (SIG CALX-320C-40 BSS).

It arrived with a 9 mm barrel in the 40 slide by mistake. (Mag was 40.)

I measured the barrel and slide all over noting differences. 40 barrel and slide is larger where you would expect it to be (I had a different P320 40 barrel also to measure diameter), so basically you would have a sloppy fit between barrel and slide. Also between cartridge and slide and barrel.

Will a 9 barrel function in a 40 slide? I have heard that it will, but I'll never have any first hand experience with that.

However, since a 9 case is about 33 thousands smaller in diameter than a 40 case, I don't think that the larger chamber in the 40 barrel is going to give back those 9 cases in any condition for reloads.

 

There is a difference between CAN and SHOULD. You shouldn’t put a 9mm barrel in a .40 slide. It may work.

Also you should get the 9mm RSA in either case. (Comes with xchange kit)

If I could get a .40 conversion kit, I would do that. However, that’s easier said than done.

I used a .40 to 9mm conversion barrel with my legion P229 because the finish of the slide didn’t match frame with conversion slide.


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