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Glock Conversion: 9x23 Winchester


Glock pistols are well known for their firepower. They are available in most popular and powerful semi-automatic pistol calibers, and their double-stack magazines hold a large number of rounds (where legal). But Glocks are not available in all powerful pistol calibers. One of the most powerful semi-automatic calibers is the 9x23 Winchester. This screaming round brings .357 magnum performance to a semi-automatic pistol and drives 124-grain bullets to 1460 fps from a 5-inch barrel, yielding 587 ft-lbs of muzzle energy.

Glock chambers several models in the powerful .357 SIG, but the 9x23 Winchester has a performance edge, and since the 9x23 Winchester case has a smaller diameter than the .357 SIG case, which is based on a .40 caliber case, you can get more 9x23 Winchester rounds in a magazine of the same length.


One nice thing about Glocks, and some other semi-automatic pistols, is that you can change calibers with a simple barrel swap. Sometimes you need to change magazines, too. In the case of the 9mm, Glock's 9mm magazines fit the company's .40/.357 SIG frames.

Lone Wolf Distributors makes several conversion barrels for the 10mm Glock 20. These include .357 SIG, .40 S&W and 9x25 Dillon, all of which are based on a 10mm/.40 caliber case, and 9mm Luger and .38 Super. These conversions use the original 10mm magazines.


The 9x23 Winchester is a long round, like the 10mm/.45 ACP, so it requires a large-framed Glock. However, there are no aftermarket 9x23 Winchester barrels for the Glock. No problem. That's what chamber reamers are for.

I started with a 6-inch stainless steel Lone Wolf 9mm conversion barrel for Glock 20, 20 SF and 40 model 10mm pistols and rechambered it with a Manson 9x23 Winchester finishing reamer. After about 20 minutes of careful reaming by hand and periodically checking the headspace, I had a 9x23 Winchester barrel for the Glock.


The Lone Wolf barrel dropped right into my Glock 20 SF with no fitting required. Six inches is longer than the original 10mm barrel's 4.6-inch length, so it looks odd, but I decided to leave it at that length for the time being, and can always cut it shorter if I want to later on. The long barrel leaves several options open, such as having it ported or threaded for whatever accessory I might want to add.

The Lone Wolf barrel does not offer full case support up to the extractor groove. This is of no concern if you're using original 9x23 Winchester brass, because it is very thick and durable and will hold up under extremely high pressure in an unsupported chamber. However, if you're using Starline 9x23 Comp brass, you'll have to watch carefully for excess bulging because it is not as strong as the Winchester brass.


The red bar indicates the unsupported portion of the case.

Magazine capacity increases when using the smaller sized 9x23 Winchester. The Glock 20 magazine holds 15 rounds of 10mm but 18 rounds of 9x23 Winchester.

Range Time

Factory 9x23 Winchester ammunition produced high speeds from the 6-inch barrel. The 124-grain JSP load clocked an average of 1,602 fps, producing 707 ft-lbs of muzzle energy, which exceeds the power of many 10mm factory loads. Factory 125-grain STHP clocked at 1,526 fps, producing 646 ft-lbs of muzzle energy.

The archetypal load for the 10mm is a 200-grain bullet traveling at 1,200 fps from a 5-inch barrel, producing 639 ft-lbs of muzzle energy. Both factory 9x23 Winchester loads beat that, although though from a longer barrel. Double Tap loads a 135-grain 10mm bullet at 1600 fps from a Glock 20, producing 767 ft-lbs of muzzle energy. The 124-grain 9x23 Winchester load is not far from that.


Handloads were loaded in Starline 9x23 Comp brass with Winchester small rifle primers. A 121-grain Hornady HAP bullet loaded to 1.245-inch overall length with 10.4 grains of VihtaVuori N105 averaged 1,538 fps, and a 135-grain round nose Black and Blue coated cast bullet loaded to 1.270-inches overall length with 9.4 grains of N105 averaged 1,445 fps. These rounds produce 635 and 626 ft-lbs of muzzle energy, respectively. These are not especially high pressure loads; they are roughly at .38 Super pressures. N105, a relatively slow powder, was used to keep pressure low while still producing high velocity, and there was no evidence of excess bulging in the unsupported region of the brass.

There was no need to change recoil springs to get the Glock to function with 9x23 Winchester ammunition. All loads tested cycled with the factory recoil spring.


Accuracy was tested with a single 10-shot group at 25 yards off sandbags. The factory JSP produced a 3.50-inch group, with nine of those in 2.25 inches. The STHP group measured 3 inches. The handloaded 121-grain HAP produced a 2.88-inch group, and the 135 grain cast bullet group measured 3.25 inches. These are all quite good, considering my less-than-perfect vision and the Glock's less-than-perfect trigger pull.

Practical Issues: Adapting to Smaller Cases

Switching any gun to a smaller cartridge might mean changes to feeding, extraction and ejection systems to maintain reliable function. The extractor now must grab ahold of something smaller, and might need adjustment to do so reliably. Or not.

The 10mm pistols have a breach face cut for the rim of these larger diameter rounds, which is .425" in diameter, according to the SAAMI manual. The 9x23 Winchester has a .394" diameter rim, just like the 9mm Luger. Thus, the smaller diameter cases have a little wiggle room on the 10mm breech face.


The extractor hook on this gun rubbed against the extractor groove of the 9x23 Winchester cartridges and held onto the cartridge tight enough to pass the shake test - the cartridge stayed in place when the slide was gently shaken. The extractor worked well with 9x23 Winchester ammunition, though it was not perfect. There were three failures to extract out of roughly 900 rounds fired. That's not bad, but indicates that tuning might be required for some guns to achieve total reliability.

I left the extractor alone. Adjustment to make it work more reliably might present problems when switching back to 10mm ammo. For example, if one adds tension to the extractor to hold the 9x23 Winchester round more firmly, it might then have too much tension to allow reliable chambering with 10mm ammo. One could have a separate extractor and spring for each caliber, and switch them when changing barrels, if desired.

Ejection was completely reliable. Cases ejected to the right, but a few went over my head. This is not unusual, at least with my experience with Glocks. My 9mm Glock 19 does the same thing from time to time.



Rechambering the barrel to 9x23 Winchester was easy, but getting the magazines to feed reliably was not. The feed lips are set to work with 10mm ammunition and are spaced wider than what they are on a 9mm magazine. For example, the 10mm magazine feed lips have a gap that measures between 0.360 inches and 0.372 inches, depending on the magazine, whereas the feed lip gap on my Glock 19 9mm magazine measures 0.333 inches. The 9x23 Winchester round measures roughly 0.384 inches in diameter at the point of the front of the feed lips. The problem is that the top round of 9x23 Winchester points at an unusually high angle from the 10mm magazine, which can result in feeding malfunctions.

Some folks have reported (via various websites) the need to modify the feed lips on their 10mm magazines to properly hold and feed 9mm and .38 Super ammunition, while others have been able to use the magazines without modification. My unmodified 10mm magazines did not feed reliably and produced many malfunctions where the nose of the bullet was too high and hit the back of the barrel hood, so-called "high nose" malfunctions.

The high nose malfunction might be eliminated if using jacketed round nose bullets, since that profile is more forgiving than the flat face of flat nose bullets. I used flat nose bullets for most of the test-firing, because they were the ideal shape to test if the nose was too high. If it was, it would jam. The round nose bullets have to be jacketed because I experienced high nose malfunctions with cast round nose bullets. They are soft enough that the edge of the hood pressed into the lead, and the round stopped.


A second type of malfunction was when the rear of the cartridge was too low to be picked up by the slide as it moved forward. The slide's stripping rail would pass over the cartridge rim and hit the middle of the case body and jam. This is called a bolt-over-base malfunction.

The angle of the top round could vary significantly depending on how many rounds were loaded. When there were three to eight 9x23 Winchester rounds in the magazine, the rear of the top cartridge was sometimes very low because the round had a very obvious downward tilt. If the downward tilt is extreme enough, the slide will pass over the cartridge rim when traveling forward.

The tilted round is caused by follower tilt. The follower is rather short and does not fill the entire length of the magazine. In fact, the 10mm follower appears to be the exact same length as the 9mm Glock followers. This leaves a gap at the rear, which certainly does not discourage follower tilt.

Tilt is not just an issue with the 9x23 Winchester ammunition. There is also rearward tilt when using 10mm ammunition in the unmodified Glock magazines. For comparison, I don't see any cartridge tilt in my Glock 19 9mm magazines.

I narrowed the width of the front portion of the feed lips by bending them slightly with a punch and tried various widths, from .358 inches down to .335 inches. This results in the 9x23 Winchester cartridge held at an angle similar to that of a 10mm round in an unmodified magazine. However, this by itself did not cure feeding problems, and this included high nose malfunctions.


I contacted the employees at Lone Wolf for their advice on modifying the magazine, and they kindly offered to modify one for me. They used a different method; they squeezed the magazine in a vise. This method bends the magazine body much lower than just at the feed lips. However, it was bent enough that the gap in the feed lips was also reduced. The gap measured .370 inches when I sent them the magazine, and it measured .346 inches when it was returned. The Lone Wolf modified magazine did feed more reliability, but it still suffered some malfunctions.

I squeezed a magazine according to their instructions and had the same result. It improved feeding reliability, but it was not perfect. I explain in some detail how to bend the magazine later in this article. One difference I noted was that the magazine modified by Lone Wolf would not drop free from the gun when the magazine release was pressed. The one I modified would.

Follower tilt was still a problem. The rear of the top round was still quite low with roughly three to eight rounds in the modified magazines. A low rear end also means a high front end, which can produce high nose jams even with narrowed feed lips. With more or less rounds in the magazine, the rear of the round was higher. This is one of the strange things about magazines, since you'd expect the angle of the top cartridge should be the same no matter how many rounds are in it, but that's not the case.

I suspected that the short length follower might be to blame, so I tried a Glock .45 magazine follower. It is the proper length and fits the front-to-back length correctly. Unfortunately, this did not cure cartridge tilt. It's possible that a properly designed follower of the correct length, and with a longer front skirt, might fix this problem.

The next modification was to bend the magazine spring. The Glock follower lies at about a 75 degree angle relative to the spring. I bent the spring near the follower until the follower was at a more-or-less 90 degree angle. This should increase the pressure to the rear and reduce the pressure to the front of the cartridges. In spite of this dramatic change of follower angle, it did not eliminate follower tilt. But it appeared to tilt less.

Bending the magazine spring helped, and produced nearly perfect (99 percent) feeding reliability when combined with magazines modified by either bending the feed lips or by squeezing. However, just bending the spring by itself did not help feeding reliability; the gap in the magazine feed lips had to be reduced as well.


Squeezing the Magazine

Lone Wolf kindly provided pictures to demonstrate how they bent the magazine. Their instructions were to disassemble the magazine and squeeze it slowly and not to over-tighten the vise, or it could break the polymer outer covering. One should allow the magazine time to sit in the vise to give the metal liner time to "form a memory."

There were several visible vise marks in the polymer outer lining located on the front half of the magazine modified by Lone Wolf, and they were most concentrated around 5/8 of an inch below the top front surface of the magazine.

I wondered when they knew the magazine had been bent "enough," but when I asked them for more details, they did not have more specific instructions. The only measurements I had were from the magazine they squeezed. I took measurements during my procedure and provide them here for intrepid individuals who might undertake this task. I'm not claiming that this will definitely work since I only tried this with one magazine. I take no responsibility for any damage that might occur to your magazine should you decide to try this method. You do so at your own risk. My advice is that you should only try bending the magazine if you can't get reliable feeding by bending just the feed lips and the magazine spring.

I measured the gap between the feed lips as I squeezed it. Please note that the gap width that the lips are moved to during the squeezing procedure was not the width they were when the magazine was released from the vise. The magazine will "spring back" when released. Thus it is important to measure the gap width during and after each squeeze to monitor progress.

I made six to seven squeezes until the gap width was similar to the one modified by Lone Wolf, and the magazine modified by Lone Wolf was squeezed many times as well. I suggest that you plan on doing this incrementally, since if you bent it too far it might be difficult to spread it out afterward. But this is certainly uncharted territory because I don't know how much internal bending occurs or is required to produce the ultimate reliable magazine, or if you can get there with this method.

Like the Lone Wolf modified magazine, I concentrated squeezing about 5/8 of an inch below the front top and at the front half of the magazine, though when I was done, I noticed that my vise jaw marks were not as dispersed as those on the magazine that they squeezed. During the procedure, I left the magazine in the vise for an hour, or hours, before it was removed and measured.

The white arrows indicate vise marks.

When in the vise, and the magazine was slowly squeezed until the gap between the feed lips was .275 inches. They sprung back to .360 inches when it was removed. When squeezed until the gap was .250 inches, it sprung back to .358 inches. When squeezed to .225 inches, it sprung back to .355 inches. I stopped there. After several trips to the range and using this magazine about 15 times, the lips spread a little and ended up at .358 inches.

These measurements should not be considered absolute. That is, if you squeeze your magazine until the gap between the feed lips is .250 inches, it might spring back to a different width than mine did. How much the gap changes might also depend on exactly where it is squeezed. So, go slowly and gradually and take measurements to monitor progress.

After all my monkeying around with the magazines, the gap between the feed lips of the two magazines that were squeezed was .346 inches (Lone Wolf) and .358 inches (my work). The unsqueezed magazine had a gap of .353 inches (lips bent with punch). These measurement are made when they are disassembled. The lips will spread just a little when the follower and spring are in place because they are under spring pressure. There was no apparent difference in the feeding reliable of these three magazines when they were equipped with a bent follower spring.

I will continue to tinker with them to see if I can achieve 100 percent reliability. However, they were nearly perfect, and sometimes I could use them up to 10 times before I would get a malfunction. Still, perfection is the goal.

Here's something you don't see every day: a Glock firing pin strike on 9X23 Winchester cases.


The 9x23 Winchester is a very powerful cartridge but is rarely chambered in currently manufactured pistols, except on special request. It is generally associated with 1911-type pistols and is well suited to target shooting, plinking, hunting and self-defense. Factory 9x23 Winchester ammunition can be difficult to find sometimes, but it certainly lives up to its potential. Handloaders can take full advantage of this round to produce high-performance ammunition with their favorite bullet.

The ability to chamber a Glock for this potent round offers Glock fans a way to enjoy all that the 9x23 Winchester has to offer. The rechambered Lone Wolf barrel was accurate and produced impressive speeds with its 6-inch length. Fans of the 10mm will argue that the 9x23 Winchester comes up short when comparing similar bullet weights and needs a longer barrel. True, but this does not diminish the impressive performance of the 9x23. It shoots flat and hits hard in the Glock conversion.

You might be one of the fortunate individuals who gets reliable feeding from unmodified magazines. If not, the magazine might need minor modification. The most effective modification for my magazines was by bending the magazine spring combined with narrowing the feed lips either by bending the feed lips themselves or by squeezing the magazine body.

Disclaimer :The author and publisher are not responsible for mishaps of any kind which might occur from the use of this data in developing your handloads. It is the user's responsibility to follow safe handloading guidelines to develop safe ammunition. You use this data at your own risk. No responsibility for the use or safety in use of this data is assumed or implied.

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