I've decided to buy a Glock, but am unsure whether to get a G19 (9 mm) or a G23 (.40 cal.). I've read where it is possible to buy a G23, and then get a 9 mm barrel for it. It seems to be the best of both worlds. A 9 mm barrel for inexpensive target shooting, and a .40 barrel for more power. My questions are, can you buy a 9 mm barrel for the G23? What about the ejectors, will they work with both? Do you need to get different magazines, and will they both fit in the same gun? Will accuracy be OK with both barrels? And, if it possible to do this, where and what company would make a good 9 mm barrel? Thanks a lot!

No. You can get a .357 Sig barrel for your G23, but the 9mm case head is way too small.

No. You can get a .357 Sig barrel for your G23, but the 9mm case head is way too small.


Since posting the original, I went on "Glocktalk" and it appears many have used a 9 mm barrel on a G23 (.40 caliber). No one mentioned the "head space" issue. Some said you need to get a converter barrel because the 9 mm diameter is smaller than the hole on the G23 slide. Some said, although not necessary, to replace the extractor and ejector as well. You will need 9 mm magazines. I don't know who is correct. Is it possible or not?

Since posting the original, I went on "Glocktalk" and it appears many have used a 9 mm barrel on a G23 (.40 caliber). No one mentioned the "head space" issue. Some said you need to get a converter barrel because the 9 mm diameter is smaller than the hole on the G23 slide. Some said, although not necessary, to replace the extractor and ejector as well. You will need 9 mm magazines. I don't know who is correct. Is it possible or not?

First, ask Glock whether doing this voids their warranty! Probably. Does that matter to you?

I haven't tried this, but I've looked into what would be required in converting a .45acp 1911 to .40 S&W.

Head space would not be a problem, since it's built into the barrels' chambers.

Magazines would be caliber specific. 9mm rounds would just fly out of .40 magazine lips. .40 rounds would not fit through 9mm openings.

I'll guess that the OD of the 9mm G-19 barrel at the muzzle is smaller than the OD of the .40 G-23 barrel. So, the 9mm barrel is too small at the muzzle end to fit the G23 slide. So, you can't buy a G-19 barrel to do the caliber conversion. The "converter barrel" means you're getting a replacement barrel bored for 9mm, but with the same Outside Diameter as the .40 G-23.

If you look at the head of a 9mm case, you'll see the primer in the center. The firing pin must be in the center of the primer. The new 9mm barrel also must be centered on the firing pin.

So, if you have a .40 pistol, and put in a 9mm barrel, the rim will be ½ mm ( .020" ) too small in radius. An extractor only grips about .030" of the rim, anyway, so you've used up a lot of distance, as MikeG meant. The extractor has some amount of travel from an empty chamber to its position with a .40 case in position. It increases tension on the extractor against the rim as the rim moves into place. You would get less tension against the 9mm rim, because the travel is less.
Would it be enough tension? Maybe - depends on the individual pistol.

I don't know how difficult it is to change the extractor out on a Glock. It's not tough on a mil-spec 1911. If it's involved, you probably won't do it, so will have wasted your money on a 9mm barrel.

I don't know what the ejector looks like on the Glock. On most pistols, it's just a stub of sheet steel that sticks up from the frame to catch on the rim as it goes by, and push it out of the port. On most pistols I've seen, the ejector is pinned in place. If the Glock's is pinned, too, it's not something that one should replace often - could loosen up the pin holes in the frame.

If it's just the right height for a .40, then the .020" smaller diameter 9mm case may clear it, and not get ejected.

So, that's my long, ignorant answer from someone who hasn't actually tried it. Hopefully, I've given some hints as to what to look for.

If you really can't make up your mind on which caliber, then order it as a kit with both barrels and all parts, all at the same time, and make acceptance contingent on your seller demonstrating that the conversion is practical and actually works.

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Since posting the original, I went on "Glocktalk" and it appears many have used a 9 mm barrel on a G23 (.40 caliber). No one mentioned the "head space" issue. Some said you need to get a converter barrel because the 9 mm diameter is smaller than the hole on the G23 slide. Some said, although not necessary, to replace the extractor and ejector as well. You will need 9 mm magazines. I don't know who is correct. Is it possible or not?

Well.... I guess it might. It shouldn't, but if the extractor has enough play, and the ejector sticks out far enough, it could.

Headspace is controlled by the barrel itself, so that is not an issue. In theory, the chamber should hold the cartridge in line with the firing pin, even though the recess in the breechface is too large for the 9mm.

Don't know whether you would need another recoil spring or not.

I would expect that the .40 magazines to be thicker than the 9mm magazines. Maybe not. I don't have both to compare.

There are a whole lot of things that CAN be done, that are probably a lot more trouble than they are worth. I'd put this into that category, and just buy a 9mm instead, if ammo cost is an issue.

I'd look into "How much .40 ammo (or reloading supplies) could you buy with the money spent on something that might not work?"

Might help in the decision making.

It sorta seems like you're trying to build a ToyoChevroDodge to pull your boat, get groceries,get 52 MPG, and go offroad where no man has gone before :confused:
Either of your choices are fine weapons in quality calibers. Buy one of them, get ALOT of range-time with it, and then consider modifications.

And if you are still not certain of your chosen calibers' ability to do massive tissue destruction with premium bullets, try this test:

I occasional take first-time gun buyers out to the hills to shoot. I go to costco and buy a couple of roasts or turkeys, and show them, first-hand the difference between a .22LR, a .38 special, a 9mm, 10mm ( what I carry), or any other caliber they are considering.

The weapon platform and the caliber are a good deal less important than one's proficiency, and regular practice will give your weapon of choice the opportunity to work for you.
I KNOW from MY experience that a calm head and a weapon that I know I can handle effectively will work for me.

My $.02...

I'd look into "How much .40 ammo (or reloading supplies) could you buy with the money spent on something that might not work?"

Might help in the decision making.

I didn't think about the cost aspect. Suspect you could get a decent .22 rimfire for not much more money than the conversion pieces, and that will save the most money of all. There's .22 rimfire uppper for Glocks, too, I believe....

I'm new to the forum so excuse me for jumping in and posting before I introduce myself. I have a G22 and purchased an extended and ported 9mm barrel for my G22 thinking I could shoot 9mm's with no problem. Reading and knowing the Glock was originally chambered for the 9mm and that there was no significant differences between the G17 and G22, I tried a 9mm barrel. I puchased the barrel and 9mm magazine and headed off to the range. After a few 100 or so rounds I noticed that it does work. The magazine seats fine, feeds smooth enough and will eject good. I say good because every once in a while it will jam with the expended brass sticking out of the port. It leads me to believe there are two reasons it won't eject properly: the extractor and the return spring. Extractors being the same, I don't see why it can't catch the 9mm as opposed to the 40. Secondly, the 40 is a hotter round than the 9mm so I'm suggesting the recoil isn't strong enough to fully recoil the slide. Or I could just be using Winchester white box and shooting crap loads. Whatever the case, it is possible but after spending $100 for the barrel and $20 for the magazines, it wasn't worth it.

East Bay, it sounds like you are getting a lot of advice from people who don't have experience with what you want, but just "think it's a bad idea". Except maybe N23.

Lone Wolf Distributors does sell 9mm conversion barrels for the G23 for $89. Yes, you do need a conversion barrel, not a G19 barrel, because the barrel diameter is different. I have one of their threaded barrels for my G23 (in .40) and I am pleased with it.

The general consensus on Glock Talk seems to be that the 9mm conversion barrel is fine for plinking at the range, but don't depend on it for defense without changing the recoil spring and ejector. (Even then probably not a good idea, just get a G19 if you want 9mm for defense).

Some have reported that the .40 magazines do work for 9mm, haven't tried it myself.

I've considered a 9mm barrel as well, but since I reload, the .357 Sig makes more sense, as it can be downloaded to 9mm levels for plinking, or loaded up for more power.

If you go with a conversion barrel, please let us know how it works out for you.

I'm new to the forum so excuse me for jumping in and posting before I introduce myself. I have a G22 and purchased an extended and ported 9mm barrel for my G22 thinking I could shoot 9mm's with no problem. Reading and knowing the Glock was originally chambered for the 9mm and that there was no significant differences between the G17 and G22, I tried a 9mm barrel. I puchased the barrel and 9mm magazine and headed off to the range. After a few 100 or so rounds I noticed that it does work. The magazine seats fine, feeds smooth enough and will eject good. I say good because every once in a while it will jam with the expended brass sticking out of the port. It leads me to believe there are two reasons it won't eject properly: the extractor and the return spring. Extractors being the same, I don't see why it can't catch the 9mm as opposed to the 40. Secondly, the 40 is a hotter round than the 9mm so I'm suggesting the recoil isn't strong enough to fully recoil the slide. Or I could just be using Winchester white box and shooting crap loads. Whatever the case, it is possible but after spending $100 for the barrel and $20 for the magazines, it wasn't worth it.

Welcome to the forum and thanks for your first-hand report. I'm surprised this works at all, so this has been quite educational. You may have saved a few people some aggravation.

You'd need a lighter recoil spring, most likely, not a heavier one, if you were to pursue this further.

you are getting a whole bunch of different stories. Your best bet and the most cost effective option is to get the Glock 26 and use that for both target practice and selfdefence. The 9mm (you can get +P and +P+ loads that provide good power) is an excellent round.