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Discussion Starter #1
Currently have 2 P226 in .40 (along with a .357 barrel).

If I wanted to convert one to 9mm, is it simply drop in a 9mm barrel?

Do I need to change out the recoil spring and guiderod?
 

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Best thing to do is purchase a conversion kit.
the diameter of the 9MM barrel is smaller that both the 40S&W and 357Sig
and would not fully seat.
 

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Discussion Starter #3
Best thing to do is purchase a conversion kit.
the diameter of the 9MM barrel is smaller that both the 40S&W and 357Sig
and would not fully seat.
I actually thought about that when I was studying the diameter of the barrels. There may not be a way to control the accuracy when that 9mm in a .40/.357 slide.
 

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Another option is to purchase a conversion barrel from Bar-Sto. With that, you’d be able to use your current slide. Of course, you’d still need a lighter 9mm recoil spring and 9mm mags.
 

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IIRC, the P226 barrel diameters are all the same for 357, 40 and 9mm. On OEM 9mm barrel will fit in a 357 or 40 slide and lock up properly. The 9mm breach face is slightly narrower (~ 0.030") than the 357/40 barrel, but many folks run the stock 9mm barrel in 357/40 slides without issue. The wider breach face of the 357 and 40 barrels means that they won't fit in a 9mm slide but that's not the direction you are going.

My recommendation would be to use a 9mm recoil spring and mags. The guide rods are the same for all cals.

Here's a thread that provides more detail: https://sigtalk.com/sig-sauer-gunsmithing/17536-barrel-conversion-tables.html
 

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This chart, also found in the Gunsmithing Sticky section spells it out. A P226 9mm barrel, "tube" diameter is the same as the .357/.40, the P229 is the one that is different.

While a 9mm barrel may be "loose" as the hood extension on the barrel will be narrower than the breech cut. By the same token the breech cut will also be .030" larger than the diameter of the 9mm cartridge case head. "Only" the Extractor tension will be holding the cartridge case head in place as the slide strips the cartridge out of the magazine.

Conversely, the Extractor is all that is holding the fired case against the breech, until the case hits the Ejector.

While is may function fine for the range, only "YOU" can determine if your life will depend on it! Using a "conversion" barrel, only increases the width of the barrels "hood extension" to fit the slide more closely. The cartridge case head, and breech cut size difference will still be a factor.
 

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Discussion Starter #7
wow! A great education! Thank you all!
 

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Just my observation, but it sounds safer, better for the weapon wear and tear, and not a lot more expensive to just buy another handgun dedicated for 9mm...??? TG
 

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I faced that same dilemma. I bought a BarSto 9MM Conversion barrel for my 357 Stainless SIG 226 some time ago. and I was VERY pleased with the results. Got a set of Wolff recoil springs as well and some magazines. It's my End of the world weapon, with barrels in 357 SIG (and 3K rounds of ammunition) and .40 S&W (With 2K rounds) plus the 9MM conversion (Which I have shot A LOT).

Great modification. Cost $240 plus fitting (which is more then people here would Pay) and I got a great pistol.
 
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Just my observation, but it sounds safer, better for the weapon wear and tear, and not a lot more expensive to just buy another handgun dedicated for 9mm...??? TG
Trust me...we have plenty of 9 shooters.

As someone else pointed out, the ability to have multi-caliber models is a huge factor for me. I have a few P229's that are 9mm/.357/.40 capable. For that model I did buy a dedicated 9mm slide with optics.

Now that I have a couple of P226's I would like to do the same barrel swap.

I also have a few P320's of varying sizes and capable of shooting 9mm/.357/.40/.45. The number one selling point of the P320 is modularity.

Having the ability to shoot multi-caliber to me is a +plus. I can shoot what I have on hand and not worry about restocking at these crazy prices. I can get a Sig P226 barrel, recoil spring and guide rod for than $200. That is a huge savings over buying a dedicated P226 in 9mm which are selling for crazy prices at the moment.

I kinda came to the realization of the benefits of multi-cal years ago with AR's. The 556 I shoot are capable to shooting the .300 with a different upper. My .308 is also capable of shooting 6.5 with a different upper. The overall cost savings of not having to buy a .300 and a 6.5 is huge. There are some wonderful 3rd party vendors that sell quality aftermarket uppers like PSA, Radical and others. I would gladly pay $400-500 for a quality upper and take the savings and buy more pistols. Pew Pew Pew.
 

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I have a multi-caliber handgun, a revolver Taurus Tracker in .22LR + .22 magnum (swap out the cylinders to change caliber). This summer it failed with a broken transfer bar in the trigger area. If this were my only .22 pistol I would have been down for 4 months that it took to get it fixed. Fortunately, I had a back up .22 and a .17 rim fire. But it demonstrates another potential negative of an "all in one" weapon without back up.
I'm not trying to argue any merits for or against swapping calibers. My P320 M-18 is supposed to be easy to change. I like my Thompson Contender and the different barrels I have.
Simply that every choice has pluses and minuses.

I do have a serious question though and that is, are there instances where the weapon is stamped, say . 357 sig, but has a .40 barrel in it, and the wrong ammunition is chambered and fired? Obviously this could be any caliber configuration. TG
 

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I do have a serious question though and that is, are there instances where the weapon is stamped, say . 357 sig, but has a .40 barrel in it, and the wrong ammunition is chambered and fired? Obviously this could be any caliber configuration. TG
While a possibility, in any weapon system, Sig marks their barrels with what it is chambered in. Here again "user" responsibility has to be "enforced".

While a .40 S&W round would likely have the projectile driven back into the case, it would not chamber far enough to be fired. A .357 Sig round would likely chamber into a .40 S&W Chamber, however if it was able to ignite, the loss of pressure from the smaller diameter projectile would likely not cycle the pistol, and there is no telling where the projectile would "go", but just not very far from the muzzle.

Situations such as substituting .300 Blackout in a .223 Remington/5.56 NATO on the other hand would, and has lead to disaster. As the .300 Blackout projectile would be driven back into the case, and have "No Where" to go, leading up to excessive pressure, and a likely blown barrel/receiver/bolt assembly.

Years ago, while in LE, our Chief would give us a loaded magazine, for malfunction training. There could be a "dummy" round, or even a .380 Auto round, in the 9mm magazine. The .380 would "fire" but not operate the action, for a "Failure to Eject" malfunction, while a "dummy" would give a "Failure to Fire". You never knew when it would happen, during the "Shoot-N-Move" exercise.
 
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Discussion Starter #15
I do have a serious question though and that is, are there instances where the weapon is stamped, say . 357 sig, but has a .40 barrel in it, and the wrong ammunition is chambered and fired? Obviously this could be any caliber configuration. TG
Great serious question with very serious consequences.

Swapping barrels takes planning and laying things out in plain view. If I am shooting 357 I make sure everything else is out of the way and put away. I find myself shooting less .40 these days so there is less risk. But there is risk especially since the .40 and .357 use the same magazines. For a "gun to go" I do leave .357 hollow points in a couple of magazines along with the .357 barrel. This applies to both the P226 and the P229. The P229 is a little more straight forward since the whole slide assembly is changed out and that has a Romeo1 Pro.

If you own multiple P320 you have to do the same planning and due diligence. A few magazines are left full of defense ammo. One is designated as house gun while the others are put away along with that ammo. Pick a caliber and stick with it. Care needs to be exercised since the 9/40/357 take the same module whereas the .45 is its own setup.

As Willard pointed out some mistakes can have disastrous consequences. That is why I have opted to swap out complete uppers vs. barrels on my AR's. My magazines for .300 are FDE, marked 300 by the manufacturer and with decals along with the upper being FDE. All black is my 5.56 set up. Still, I put tags on the rifle as a "pause" to make sure the ammo matches the barrel before inserting into magwell.
 
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As Willard pointed out some mistakes can have disastrous consequences. That is why I have opted to swap out complete uppers vs. barrels on my AR's. My magazines for .300 are FDE, marked 300 by the manufacturer and with decals along with the upper being FDE. All black is my 5.56 set up. Still, I put tags on the rifle as a "pause" to make sure the ammo matches the barrel before inserting into magwell.
I did this to our Handguns and ARs.
-Handguns: FDE grips for the wife (9mm) and ODgreen for me (.40)
-ARs: Pink for the wife and FDE & ODgreen for me. Doesn't matter anyway because we both shoot one caliber (.223/5.56). Just an excuse to put on different colors. :p
 
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