Glock conversion question

[Jose]

I know you can convert a .357 Sig to shoot .40 S&W and vice versa but what about 9mm to .357 Sig? Any ideas?

[Jose]

No thoughts on this?

[HOOCBB]

It would be the same as if you were to try to convert a 9mm to a .40. You can use the same frame, but you would need the .40 ejector which is integral in the trigger mechanism housing.

I don't think you would be able to use the same slide as I believe the .40 and .357 barrels are a bit larger in diameter than the 9mm. So, you would be looking at a new slide as well.

Since the .40 ejector will not work properly with a Glock factory 9mm barrel, you would have to change the housing out every time you switched calibers.

I'm not sure it would be worth all that work to do it. If you have to get a new slide, you might as well get the whole pistol.

[Tannerm]

Um, I thought converting a 357 to 40 and vice versa was just a barrel change. They use the same mag.

[HOOCBB]

Um, I thought converting a 357 to 40 and vice versa was just a barrel change. They use the same mag.

Correct, but he was asking 9mm to .357 Sig.

[ThreeFingerPete]

I know you can convert a .357 Sig to shoot .40 S&W and vice versa but what about 9mm to .357 Sig? Any ideas?

Why bother? 9mm +p+ is pretty close to .357 sig performance, with higher capacity in, the mag, and the ability to shoot cheap stuff without changing barrels.

[Fry86]

From a Glock point I think its just a simple barrel, slide, and mag change.

Sent from a bathroom.

[Jose]

Yes I was asking about a 9mm to .357 conversion. HOOCBB's explanation makes sense and explains why I did not see any conversion's offered. Not worth the trouble if I have to replace the slide to do a conversion.

I'll have to research that Adam, I'd like the cost effectiveness of the 9mm but would prefer the ballistics of the .357 Sig if I needed it. When you say the 9mm +P+ is pretty close to the .357 Sig performance wise, are we just talking about velocity? Or have you seen test with specific bullets with examples of expansion in test media?

[Nash B.]

I'll have to research that Adam, I'd like the cost effectiveness of the 9mm but would prefer the ballistics of the .357 Sig if I needed it. When you say the 9mm +P+ is pretty close to the .357 Sig performance wise, are we just talking about velocity? Or have you seen test with specific bullets with examples of expansion in test media?

.357 Sig is just a 9mm bullet in a necked-down .40 S&W case. So if you get .357 Sig velocity (for a given bullet) from 9mm +P+, it's going to perform exactly like .357 Sig.

[Tannerm]

Correct, but he was asking 9mm to .357 Sig.

dammit... I didnt read it all lol. I focused on the .40 and nothign else past it.

[IHaveAMustang]

All I know is you can go from .40 down to 9mm with just a barrel change. Which is awesome...I bought dirt cheap KCI Glock 17 mags and have a cheap firing Glock. Plus got one with a threaded barrel so I can suppress it someday

[Jose]

All I know is you can go from .40 down to 9mm with just a barrel change. Which is awesome...I bought dirt cheap KCI Glock 17 mags and have a cheap firing Glock. Plus got one with a threaded barrel so I can suppress it someday

If I'm understanding things right, starting with a Glock 9mm you can't convert to .40 S&W/.357 Sig because of the extractor. Starting with a .40 S&W/.357 Sig wouldn't be a problem a problem as it's extractor can handle the 9mm.

So I'm not getting the 9mm +P+ is the same as a .357 Sig. Why even bother making a new caliber? I did find some interesting threads comparing ballistic performance between the calibers and in some test the .357 Sig appears to edge it out consistently and in others they are fairly close

[HOOCBB]

If I'm understanding things right, starting with a Glock 9mm you can't convert to .40 S&W/.357 Sig because of the extractor. Starting with a .40 S&W/.357 Sig wouldn't be a problem a problem as it's extractor can handle the 9mm.

So I'm not getting the 9mm +P+ is the same as a .357 Sig. Why even bother making a new caliber? I did find some interesting threads comparing ballistic performance between the calibers and in some test the .357 Sig appears to edge it out consistently and in others they are fairly close

Well, you can't use a Glock 9mm (say from a model 26) barrel in a .40 (model 27). In order to do this, you have to use a conversion barrel, which offsets the chamber ever so slightly so the .40/.357 extractor/ejector will interface with the round correctly.

Since the .40 and 9mm recoil springs are the same part number, you can use the same one with both rounds. However, some people will recommend using a different spring for each caliber due to different round characteristics.

Also, the 9mm +P+ round is not as easy to acquire as a .357 Sig. In addition, not all 9mm chambers are rated to withstand the higher pressures, so I would proceed with caution if you are thinking about using a 9mm +P+.

[ThreeFingerPete]

If I'm understanding things right, starting with a Glock 9mm you can't convert to .40 S&W/.357 Sig because of the extractor. Starting with a .40 S&W/.357 Sig wouldn't be a problem a problem as it's extractor can handle the 9mm.

So I'm not getting the 9mm +P+ is the same as a .357 Sig. Why even bother making a new caliber? I did find some interesting threads comparing ballistic performance between the calibers and in some test the .357 Sig appears to edge it out consistently and in others they are fairly close

Because few gun manufacturers are going to tell you that it's okay to run extremely hot loads, even if the firearm is the exact same design as the model that fires a much higher pressure load.
9mm maximum pressure = 34,000psi So even loaded ultra hot, a 9mm that isn't beyond it's maximum is still easier on the gun many .357 sig rounds.
.357 sig maximum pressure = 40,000psi
+p refers to + pressure. In most rounds, a "+P" designation will be an approximate 10% increase in pressure. "+p+" simply means beyond "+p" but not as much as a proof load (a cartridge that is approximately %30 higher than "normal" used to verify the function of a gun)
9mm +p+ falls higher than average of .357 sig defense ammo velocities.
Buffalo Bore 9mm +p+ ammunition:
115gr @ 1400fps = 500ft/lb

357 Sig 115 gr FTX® Critical Defense
115gr @ 1239fps = 389 ft/lb


357 Sig 115gr CORBON Self-Defense JHP
115gr @ 1500fps = 575ft lbs

And the hottest I've seen, this is
357 Sig 115gr. Nosler JHP Buffalo Bore
115gr @ 1550fps 614 ft. lbs


You can have EXTREMELY good performance out of a .355 projectile from either 9mm or .357 sig. The downsides to .357 sig are man, such as the huge expense of training ammunition, lower ammo availability, bigger PITA to reload, lower magazine capacity compared to 9mm, etc.