.40 in a 10mm Glock

[The Evangelist Cowboy]

Anyone ever try this? I have a Glock 29 in 10mm and the ability to shoot .40 would be a big saver in the budget since I dont reload 10mm, I've seen several vids and it seems like works just fine, with one video commentator saying he knows people in competition who put several thousands of rounds of .40 through their Glock 20's.

 

[PO2Hammer]

I've done it too. In a 20 and 29. Worked perfectly. Then I got smart and bought KKM conversion barrels for both.
Both guns become very nice target guns with 40 ammo. Much like a 357/38 revolver. (although I'm sure someone is going to tell me it's not)

 

[The Evangelist Cowboy]

Why the extra barrel its the same caliber?

 

[wally]

Why the extra barrel its the same caliber?

Its kind of like shooting .38 Special in a .357 Mag, if you do it a lot you can get erosion of the chamber in front of the shorter cartridge that can lead to extraction issues when you go back to the longer cartridge. If you plan to do it a lot, the "conversion" barrel is the way to go.

 

[mcb]

It works but you are head spacing off the extractor rather than the case mouth. In theory a round could get ahead of the extractor and into the chamber and would not fire. You would have to poke it out of the chamber with something. A 40S&W conversion barrel would be more reliable but not required.

 

[JohnKSa]

It works, but it's not ideal and can, in the worst case, cause serious problems.

Much like a 357/38 revolver. (although I'm sure someone is going to tell me it's not)

It's not.

Two reasons.

1. Revolver cartridges like the 357/38 headspace on the rim. A shorter cartridge is a non-issue since it will still headspace as it should. In an autopistol, a cartridge that is shorter than it should be, headspaces on the extractor. In general, extractors are not made to take a lot of that kind of stress.

2. Unlike revolvers which have a smooth transition in the chamber (since the cartridge headspaces on the rim and not the case mouth) autopistol chambers have a sharp step at the front of the chamber. When shooting the firearm with the proper cartridge, the bullet is forward of this sharp step, but with a shorter cartridge, the bullet can hit that sharp step. When that happens, material can be shaved off and build up at the front of the chamber. In the worst case, that can lead to a partial obstruction which could blow the gun.

If you really can't afford a conversion barrel and really need to shoot .40 in your 10mm autopistol, try to limit how much you shoot through it in any given shooting session and be sure to clean the chamber thoroughly and check your extractor carefully after every shooting sesson. Do not EVER shoot a bunch of .40 through the gun and then switch back to 10mm without cleaning the chamber thoroughly. If there is a buildup, it may prevent the gun from going fully into battery which could lead to an out-of-battery discharge--something to be avoided.

I know a lot of people do it and get away with it, but that doesn't mean it's a good practice or that it is completely without risk.

In general, your owners manual will tell you exactly what ammunition is suitable for your gun. For example, I have a .357Mag revolver and the manual explicitly states that it may also be used with .38Spl or .38Spl +P.

The Glock manual explicitly states that only ammunition "in the caliber of your pistol" should be used and then, for additional emphasis provides a short table which lists only 10mm as being suitable for the Glock 20.

 

[The Evangelist Cowboy]

Thanks for the wise words all, I may just get rid of it and move onto the .45 model 36

 

[Fine Figure of a Man]

Thanks for the wise words all, I may just get rid of it and move onto the .45 model 36

I have a G36, it's OK but I would recommend getting the G30.

 

[mcb]

It works, but it's not ideal and can, in the worst case, cause serious problems.It's not.

Two reasons.

1. Revolver cartridges like the 357/38 headspace on the rim. A shorter cartridge is a non-issue since it will still headspace as it should. In an autopistol, a cartridge that is shorter than it should be, headspaces on the extractor. In general, extractors are not made to take a lot of that kind of stress.

2. Unlike revolvers which have a smooth transition in the chamber (since the cartridge headspaces on the rim and not the case mouth) autopistol chambers have a sharp step at the front of the chamber. When shooting the firearm with the proper cartridge, the bullet is forward of this sharp step, but with a shorter cartridge, the bullet can hit that sharp step. When that happens, material can be shaved off and build up at the front of the chamber. In the worst case, that can lead to a partial obstruction which could blow the gun.

If you really can't afford a conversion barrel and really need to shoot .40 in your 10mm autopistol, try to limit how much you shoot through it in any given shooting session and be sure to clean the chamber thoroughly and check your extractor carefully after every shooting sesson. Do not EVER shoot a bunch of .40 through the gun and then switch back to 10mm without cleaning the chamber thoroughly. If there is a buildup, it may prevent the gun from going fully into battery which could lead to an out-of-battery discharge--something to be avoided.

I know a lot of people do it and get away with it, but that doesn't mean it's a good practice or that it is completely without risk.

In general, your owners manual will tell you exactly what ammunition is suitable for your gun. For example, I have a .357Mag revolver and the manual explicitly states that it may also be used with .38Spl or .38Spl +P.

The Glock manual explicitly states that only ammunition "in the caliber of your pistol" should be used and then, for additional emphasis provides a short table which lists only 10mm as being suitable for the Glock 20.

1. The firing pin hitting the primer is really no harder on the extractor than the extractor pulling the case from the chamber. Think about how fast that extractions happens and the fact that there is still pressure/friction in the cartridge and the stress on the extractor when the case suddenly stops on the ejector and pivots around the extractor. The firing pin hitting the case head spaced on the extractor is rather trivial.

2. I have a S&W 610 that I have put probably close to 20,000 rds of 40S&W through it, plated, jacketed and lead over the years and never had any of the issues you mention in point two. Since it's a revolver I am head spacing on the moonclip not the extractor so I don't have that issue but I am still firing 40S&W in a 10mm chamber that is a proper 10mm chamber. It will fire 10mm Auto without the moonclip head spacing on the case mouth.

 

[jmr40]

I've done it enough to know it'll work in an emergency. And it works VERY well. I've had zero issues and the POI and accuracy didn't change. But it isn't something I make a practice of.

But I can get 10mm ammo cheaper than 45 and only slightly more than 40 S&W. I also have a Glock in 9mm that functions exactly like the 10mm for cheap practice. I like that idea better than a 40 barrel for the 10mm.

 

[JohnKSa]

I have a S&W 610 that I have put probably close to 20,000 rds of 40S&W through it, plated, jacketed and lead over the years and never had any of the issues you mention in point two.

And you shouldn't expect to either because the manual explicitly states that is acceptable practice.

Here's an excerpt from the S&W revolver manual:

Additional ammunition calibers can be fired from the following list of select calibers.
Caliber on Barrel----- Can also Fire
.45 Colt------------------.45 Schofield, .45 S&W .45 S&W .45 Schofield
.44 Magnum-----------.44 Special
.357 Magnum---------.38 Special, .38 Special +P
.22LR-------------------.22L, .22 Short, .22CB, .22BB (in revolvers only)
10mm------------------.40 S&W (in revolvers only)​

It's worth pointing out that they differentiate between revolvers and autopistols. Wonder what that's all about?

 

[mcb]

And you shouldn't expect to either because the manual explicitly states that is acceptable practice.

From the S&W manual:

Additional ammunition calibers can be fired from the following list of select calibers.
Caliber on Barrel Can also Fire
.45 Colt .45 Schofield, .45 S&W .45 S&W .45 Schofield
.44 Magnum .44 Special
.357 Magnum .38 Special, .38 Special +P
.22LR .22L, .22 Short, .22CB, .22BB (in revolvers only)
10mm .40 S&W (in revolvers only)​

Then why would you expect to then have the problems you stipulate in your point 2 in any other 10mm chamber firing 40S&W? S&W puts a standard 10mm Auto chamber in the 610 Revolver minus only the rifling in the cylinder throat. The difference in chamber length is only .142 inch. Unless you are shooting super light/short bullets most 40 S&W bullets have enough bearing area to still be well in the case keeping the bullet concentric when they enter the throat. I just don't see the end of the chamber as that big of a deal given the number of people shooting 40S&W in 10 chambers, revolver or otherwise.

 

[JohnKSa]

I don't know the specific differences between the S&W 610 revolver and the S&W 10mm autopistols that prompted S&W to make the differentiation in the owner's manual. Obviously there IS some difference or they wouldn't bother to explicitly point it out and also make it clear that using .40S&W in a 10mm is only acceptable in their revolvers.

That's a direct quote from the S&W manual, why not ask them? I've already given my take.

 

[PCFlorida]

I don't know the specific differences between the S&W 610 revolver and the S&W 10mm autopistols that prompted S&W to make the differentiation in the owner's manual. Obviously there IS some difference or they wouldn't bother to explicitly point it out and also make it clear that using .40S&W in a 10mm is only acceptable in their revolvers.

That's a direct quote from the S&W manual, why not ask them? I've already given my take.

And your quote is exactly correct.

 

[mcb]

I don't think it has anything to do with the chamber mouth. Probably more to do with head space and reliability issues than 40S&W bullets jumping the length of a 10mm chamber.


Top: 40S&W chamber from an XD-40, Bottom 10mm Auto Chamber from a S&W 610. Very similar case mouth.

 

[JohnKSa]

I don't think it has anything to do with the chamber mouth. Probably more to do with head space and reliability issues than 40S&W bullets jumping the length of a 10mm chamber.

Well, one thing we know for sure is that the manufacturer recommends against it. You don't like my explanation, so that frees you to make up an explanation you like better. But it doesn't change the fact that Glock says not to do it and S&W says that it's only acceptable in revolvers.

Another interesting data point:

http://stevespages.com/pdf/colt_mkiv_series_80_&_90_pistols.pdf

On page 2 of the manual, Colt specifically lists .40S&W as being unsuitable for use in their 10mm 1911.