40 S&W to .357 Sig

[BJung]

With the FBI's adoption of the 9mm again, it seems that a lot of shooters are doing the same and dropping the .40, thinking it's now obsolete. Besides .40 S&W still being an effective round, having the option of shooting a .357 Sig is a great alternative upgrade since it would be like shooting a 125gr. .357mag load as a SD load. Has anyone bought a barrel to drop in, have that had any issues, and did they have to buy additional springs..for the conversion?

 

[starling]

I have done a few. Some platforms are more forgiving than others. 357sig is harder on the gun if you are shooting true power 357sig. I tend to play with the springs weights and also use a buffer if possible. You are essentially turning a 40S&W into a Magnum autoloader. I wont even try it on certain designs.

 

[BJung]

I have a BHP 40 S&W. Will a .357 damage the frame? That's the last thing I want..

 

[starling]

I have a BHP 40 S&W. Will a .357 damage the frame? That's the last thing I want..

I wouldnt convert a Hi-power but its been done. Design is almost 100 years old and never meant for those kind of pressures. You could protect the frame. Use a buffer and increase the hammer spring, adjust the recoil strength. Typical stuff. If you can get a threaded barrel with a compensator that would help but I dont know what is out there for Hi-power these days. Its more about the barrel lockup and timing than it is about frame battering.

 

[fxvr5]

I wouldnt convert a Hi-power but its been done. Design is almost 100 years old and never meant for those kind of pressures.

What pressure are you talking about?

Let's apply that logic to another old gun. The 1911 is over 100 years old and was designed around a 21,000 psi cartridge, the 45 Auto. God forbid it should be chambered with a higher pressure round. I mean, the 9mm has a max pressure of 35,000 psi. Certainly that would be hard on that 100+ year old design.

 

[starling]

What pressure are you talking about?

Let's apply that logic to another old gun. The 1911 is over 100 years old and was designed around a 21,000 psi cartridge, the 45 Auto. God forbid it should be chambered with a higher pressure round. I mean, the 9mm has a max pressure of 35,000 psi. Certainly that would be hard on that 100+ year old design.

1911 can handle 9mm fine. Full power 10mm is another story. I dont even like the 1911 design in 40S&W to be honest. JMB would most likely never have designed the 1911 for those cartridges. There are a few workarounds that help but that all you can do.... help things a little.

Best 357sig conversion I can think of off hand would be a Glock 20. This is regarding hot 357sig loads though....which is the whole point IMO.

 

[BJung]

I own both a BHP 9 and 40 and the 40 is slightly beefier. On another site, The Pistolsmith, some have converted even their 9mm to a .357Sig (?) and they haven't blown apart. I just want a handgun that can is more diverse by being able to shoot 2 calibers and the second being a .357 Sig as a great SD load. I don't plan to shoot the converted cartridge often and if so the hottest loads would be shot during a test loading while practice loads would be more mild. I just don't my cherished handgun to break after shooting only 100-200 rounds through it.

 

[fxvr5]

1911 can handle 9mm fine. Full power 10mm is another story. I dont even like the 1911 design in 40S&W to be honest. JMB would most likely never have designed the 1911 for those cartridges. There are a few workarounds that help but that all you can do.... help things a little.

Best 357sig conversion I can think of off hand would be a Glock 20. This is regarding hot 357sig loads though....which is the whole point IMO.

Repeat, what pressure are you talking about?

The 9mm has a 35,000 psi pressure and the 10mm has a 37,500 pressure. That's not very different, and 9mm +P is 38,500 psi. So the 1911 can't handle a 10mm then it must be even worse with a 9mm +P.

 

[starling]

I own both a BHP 9 and 40 and the 40 is slightly beefier. On another site, The Pistolsmith, some have converted even their 9mm to a .357Sig (?) and they haven't blown apart. I just want a handgun that can is more diverse by being able to shoot 2 calibers and the second being a .357 Sig as a great SD load. I don't plan to shoot the converted cartridge often and if so the hottest loads would be shot during a test loading while practice loads would be more mild. I just don't my cherished handgun to break after shooting only 100-200 rounds through it.

it would take more than 100-200 rounds to kill it if you did it right. You definitely want to use the 40 version of the hipower. Slides are stronger and I think they use an extra locking lug if I am not mistaken. Play with the springs and use a buffer and its doable for light use. Keep an eye on the locking surfaces for peening or cracking. You will get signs if its not holding up. Converting a 9mm to 357 sig is silly IMO. Probably wont blow up but its going to beat itself to death fairly quickly if you actually shoot it a good bit.

 

[brmiller]

My two 10mm 1911s handle 10mm just fine. But I built them specifically for 10mm.

 

[WrongHanded]

I have converted three guns.

A Sig P224 originally in .40S&W. I dropped in a factory .357Sig barrel.

A G23 gen 4, using a KKM barrel.

A G22 gen 4, also using a KKM barrel.

I also purchased a G33 Gen 4, which is just a G27 with a .357Sig barrel. But do have a KKM .40S&W conversion barrel for it.

Nothing else about the guns needed to be changed. .40S&W magazines feed .357Sig just fine in my experience. Though the reverse is not always true.

The additional pressure going from 35,000 PSI in the .40S&W, to 40,000 PSI in the .357Sig, is contained by the chamber and barrel. And to a smaller degree by the lockup of the barrel and slide. 9mm +P is rated at 38,500 PSI, so if the gun is designed to handle 9mm +P and .40S&W, it can probably handle the additional 1,500 PSI of the .357Sig.

The other issue could be slide velocity. A lighter bullet being pushed faster can cause higher slide velocity. Is that an issue? Maybe, or maybe not. Run some data through this calculator to compare the two cartridges.

https://shooterscalculator.com/recoil-calculator.php

My .357Sig range load is a 124gr FMJ TCFP running at 1,425fps from that converted G23. I probably have a couple thousand of those through the gun now, with zero problems so far. The G22 probably has close to the same. That's not a huge volume of ammunition, so longevity is still a question, but who says you have to run full tilt ammo. You could run 125gr at 1350fps (SD factory levels) and have no issues at all.

I've got no personal experience with the BHP, but it must be a modern firearm. I can't see any reason it wouldn't work safely, at least in relatively small volumes of ammo. You might install a new recoil spring, and track your round count. This is what I've begun to do with the Glocks. I plan to switch the RSA at 3K just to be safe.

 

[starling]

Sigs, Glocks, Hk USP are pretty conversion friends platforms. XDs used to offer 357sig... not sure why they axed them.

 

[trackskippy]

I had a number of SIG's in 357SIG, and did the reverse, and bought 40 S&W barrels for them. All that did was solidify my thinking that "conversions" were just a waste, although I got out of them at a good time and doubled my money on the unopened cases of 40 I bought to go along with the barrels.

I also had a Glock 31 in 357SIG, and basically, that gun got me out of 357SIG, as I came to realize that 9mm was a lot more versatile and 9MM +P+ was pretty close to the factory 357SIG loads at the time, so I got the best of all worlds.

357SIG was beating the underside of the slide to death on my 31, and showed no sign of stopping. The locking block was pretty heavily peening the slide. Funny thing was, I still have a 17 that has more rounds of 9mm +P+ through it (same pressure as the 357SIG), and it just shows some finish wear in the same spot the 31 was peening.

I did end up putting an LWD 40-9 9mm conversion barrel in the 31 and ended up putting a lot more 9mm through it than 357SIG. The peening also stopped when I did.

The SIG's, two P226's, two P229's, and a P239, all seemed to handle the round without any issue and all shot well with it.

Personally, If I was going to go with a barrel swap, Id go with one in 9mm, for a couple of reasons. 9mm is pretty much always the cheapest, so you get to shoot more for the same money. And that goes for reloading too. 357SIG is expensive, both in loaded ammo and components. 9mm is just a lot more versatile too. 357SIG is basically a one-trick pony. If you want or feel the need for something hotter, you can always shoot +P+ and you'll be in a similar range as the 357SIG.

Other than the 357's "bark", I doubt you could even tell what you were shooting if someone handed you the same model gun in either 9mm or 357, and didn't tell you what it was. They both shoot very much the same, the 357 just has that bark to it.

 

[hso]

Considering the value of real HPs I wouldn't put one at risk for anything. Look to the clones to play with.

 

[BJung]

The two primary bullets I plan to shoot through this Sig or any other .358" bore matching bullet are the 125gr GD and cast hp, powder coated, gas checked bullets. I'll find the right alloy for the higher chamber pressure possible. So would others agree that a hot 9mm load is close to a .357 Sig? Please reply, if so, I'll save my money and conduct some experiments with the cast bullet combination I mentioned first, instead.

 

[loadedround]

I purchased a Sig P229 last year in 357 Sig and since tthe 357 Sig cartridge is basicly the 40 S&W case necked down to .357'', I decided to buy a 40 S&W barrel from Sig. It was a drop in conversion and used the same magazine (mag is marked both 357 Sig/40 S&W) as the 357 Sig, and it functioned perfectly. So yes it's possible and works well in a Sig.

 

[.308 Norma]

I purchased a Sig P229 last year in 357 Sig and since tthe 357 Sig cartridge is basicly the 40 S&W case necked down to .357'', I decided to buy a 40 S&W barrel from Sig. It was a drop in conversion and used the same magazine (mag is marked both 357 Sig/40 S&W) as the 357 Sig, and it functioned perfectly. So yes it's possible and works well in a Sig.

That was my experience as well - I had a Sig P229 357 Sig, bought a 40 S&W barrel from Sig, dropped it in, and it "functioned perfectly" with no other changes.

 

[starling]

I purchased a Sig P229 last year in 357 Sig and since tthe 357 Sig cartridge is basicly the 40 S&W case necked down to .357'', I decided to buy a 40 S&W barrel from Sig. It was a drop in conversion and used the same magazine (mag is marked both 357 Sig/40 S&W) as the 357 Sig, and it functioned perfectly. So yes it's possible and works well in a Sig.

Easier to get away with in a Sig as they designed the cartridge. They had the whole 357sig figured out of the bat with the original 229. To this day I believe they still offer the best platform for 357sig. Something like A Glock I would only go to the full size G20 frame (even for 40S&W). Platforms play into this. I have done a couple Sigma conversions in 357sig. While a Sigma 40S&W will run fine for a long, long time...put that gun in 357sig and you will eventually crack the frame below or around the locking block unless you play with the design a little to give the platform a little help. 357sig Ruger P94 I did was a straight up barrel swap for the most part.....so far!

357sig is one of those cartridges people seem to underestimate. Its a very high pressure round (40-44,000 PSI) that puts a lot of stress on a pistol even compared to a 40S&W. Lots of people do straight barrel swaps which can work for a short time. They neglect to check critical areas for wear or signs of damage and either end up with broken guns or never shoot enough of hot 357sig for it to matter. Its not a given that a pistol designed around 40S&W will be able to handle 357sig. Again... some platforms are better than others.

I am comfortable saying if you have an extremely bomb proof and durable 40S&W pistol it might be a good candidate for 357sig (Your Ruger P series, HK USP etc). Stuff like Hi-powers, Beretta 92s (dont do it), and even 1911 stuff... its best to be careful and take your time. Beretta PX4 40S&W might be a good candidate but I dont think they ever tried it.

Personally I love the 1911 platform but would like to see someone come out with a better locking system for these High Pressure rounds. Maybe bring back the Mexican rotating barrel 1911. I dont see the point in putting the time and money into a 1911 only to beat it to death with overpowered round for the design. I also dont see the point in shooting watered down loads in high pressure rounds just to say you have a pistol chambered for this or that. Better to just get a platform capable of handling full power. Its kind of like having a 357 Magnum that you can only shoot 38 special out of so you dont damage the gun prematurely.

 

[herrwalther]

Repeat, what pressure are you talking about?

The 9mm has a 35,000 psi pressure and the 10mm has a 37,500 pressure. That's not very different, and 9mm +P is 38,500 psi. So the 1911 can't handle a 10mm then it must be even worse with a 9mm +P.

According to CIP, max pressure for 357 SIg is 44,240 PSI. That pressure is another ball park compared to 9mm and 40. I would not want to have that kind of pressure in an old design that was not built for it.

 

[WrongHanded]

The two primary bullets I plan to shoot through this Sig or any other .358" bore matching bullet are the 125gr GD and cast hp, powder coated, gas checked bullets. I'll find the right alloy for the higher chamber pressure possible. So would others agree that a hot 9mm load is close to a .357 Sig? Please reply, if so, I'll save my money and conduct some experiments with the cast bullet combination I mentioned first, instead.

Just so you know, .357Sig doesn't use 0.358" diameter projectiles. It uses 0.355", like 9x19mm.

 

[Howland937]

The two primary bullets I plan to shoot through this Sig or any other .358" bore matching bullet are the 125gr GD and cast hp, powder coated, gas checked bullets. I'll find the right alloy for the higher chamber pressure possible. So would others agree that a hot 9mm load is close to a .357 Sig? Please reply, if so, I'll save my money and conduct some experiments with the cast bullet combination I mentioned first, instead.

A hot 9mm could be made comparative to the .357 SIG, I'm sure. 9mm +P+ is a thing, but since there's no industry standard/SAAMI specs for pressure, then you're really just loading 9mm+P above max (38,500)

So if we're talking about shooting ammo in chambers (and brass) at 40,000+ psi, I'd trust the barrel and the brass that was actually designed to handle it.

 

[WrongHanded]

According to CIP, max pressure for 357 SIg is 44,240 PSI. That pressure is another ball park compared to 9mm and 40. I would not want to have that kind of pressure in an old design that was not built for it.

CIP calls it the .357 SIG, and SAAMI calls it the .357 Sig. Note the capitalization. CIP has a higher MAP than SAAMI.

 

[starling]

According to CIP, max pressure for 357 SIg is 44,240 PSI. That pressure is another ball park compared to 9mm and 40. I would not want to have that kind of pressure in an old design that was not built for it.

Frame cracking can be dealt with pretty easily... Springs, Buffers, Compensators, even porting a barrel. The locking system is a whole different matter. Then you throw in slide design. Most semi auto locked slides you have a weak point under the ejection port by back by the extractor. So you have to keep an eye on that area along with the barrel to slide locking surfaces.

Of course beefing up the slide help a lot of this. Thats kind of why a 1911 style LAR grizzley can handle 45 win mag where as something like a 460Rowland conversion can only be done with certain makes of 1911s and need a big Compensator and new recoil system so work. How well something like the 460 can work would be interesting but I have never seen an endurance test on one probably due to ammo cost.

Funny thing is something like A Hi-point would be fairly easy because the slides are so heavy and the is no locking system other than static slide weight. At that point the locking system is not a concern (there isnt one), The frame is not really a concern (polymer frame with basically a Zamak buffer). Maybe weight up the slide a little to hold the (pressure if even necessary) and throw in a 357sig barrel. Hi-points have a lot of wiggle room. Biggest potential issue I can think of is the steal barrel coming loose inside the Zamak barrel housing.

 

[WrongHanded]

Okay, I ran some number comparing a 155gr JHP in .40S&W to a 125gr JHP in .357Sig. Both loads are using BE-86 (you can find the loads on Alliant's website). I rounded the velocities up slightly, the .40 by 7fps, the .357 by 12fps (I've used that load and chrono'd it). The gun weight is based on a partially loaded full-sized Glock, right at 2lbs. Compare the various recoil numbers. There's not enough difference to concern anyone.

 

[Lennyjoe]

I’ve converted a G32 and P226 to .357 Sig and keep the .40 cal factory barrels as spares just in case.

This Sig was .40 Cal factory and I purchased the new .357 Sig barrel for a little over $100 online.