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Pistol Powerhouse: The 9x23 Winchester

9X23_winchester_FThe 9x23 Winchester cartridge is a powerhouse round that few have heard of. Too bad. It delivers .357 Magnum performance in a semi-automatic pistol.

9X23_winchesterIn simplistic terms, the 9x23 Winchester is a stretched out 9mm Luger (pictured). Both are tapered cartridges with nearly identical neck, head and rim dimensions. The 9x23 case is 4mm longer, but more importantly the 9x23 operates at much higher pressure than the 9mm Luger. Winchester's 9x23 brass has an extra-thick case wall that allows this cartridge to run at high pressure without concern of a case blowout in the unsupported region of a conventional, non-ramped barrel.

The 9x23 is also a longer cartridge overall, and requires a full-sized pistol frame whereas the 9mm Luger can be housed in small-frame pistols.

The 9x23's Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) maximum average pressure limit is 55,000 pounds per square inch (psi), the same as a .223 Rem. rifle round! Compare that to the 9mm Luger's 35,000 psi and its +P limit of 38,500 psi. The 9x23's older cousin, the .38 Super +P, whose case is the same length of 0.900" (Figure 2), has a SAAMI pressure limit of 36,500 psi.

9X23_winchester_38-superThe 9x23's SAAMI maximum cartridge overall length (COL) is 1.300" compared to the .38 Super's 1.280". The 1.300" length is a bit long to fit in some magazines that house the .38 Super. I tried some 1.300" length 9x23 rounds with round nose bullets in two Chip McCormick 1911 .38 Super magazines. They fit, but not when the bullet was loaded just 0.005" longer (1.305"). That's not much margin for error. The 1.300" round would not fit in a Para Ordnance .38 Super double column magazine. The Winchester factory rounds with flat nose bullets measure at 1.230 — 1.245", which is typical for this bullet design in the .38 Super as well. In practical terms, it's wise to load them similar to the .38 Super's COL to fit in similar magazines.

Factory Ammunition

Winchester offers two factory 9x23 loads, a 124-grain SP bullet at 1460 fps, and a 125-grain Silver Tip HP at 1450 fps. These loads yield 587 and 583 foot pounds (ft.-lbs.) of muzzle energy, respectively. This equals most current .357 Magnum factory 125-grain loads from a 4" barreled revolver. COR-BON offers three loads in the 9x23 Winchester, a traditional 125-grain JHP at 1450 fps, a 100-grain Pow'RBall at 1600 fps, and a 125-grain Barnes XPB copper HP at 1350 fps. RBCD loads a 60-grain Total Fragmenting SP bullet at 2625 fps. That's it. If you want something different, you have to load your own.

9X23_winchester_1Three factory rounds were tested: two Winchester loads and the COR-BON 100-grain Pow'RBall (pictured), fired from a custom Caspian pistol with a 5" Nowlin 9x23 barrel. Both Winchester loads lived up to their published velocities; the 124-grain SP round exceeded it. The COR-BON load was a little shy of its published speed. Only two rounds of Pow'RBall were test fired. The cases showed excess bulging and no more of these rounds were fired due to safety concerns.

The red bar indicates how much of the case ahead of the extractor groove is not supported.

The COR-BON ammunition was loaded in Starline 9x23 Comp cases (footnote 1), Starline's version of the 9x23 Winchester. These cases bulged excessively in the unsupported region of the Nowlin barrel. The test gun has a conventional feed ramp and the Nowlin barrel's chamber leaves a portion of the case unsupported. High pressure can make the brass expand too far and bulge in the unsupported region. If the pressure is too great, the case can rupture exposing the shooter (and gun) to very dangerous case fragments and a blast of hot, high pressure gas. Starline brass is discussed in more detail later.

Handloading the 9X23

The limited selection of factory 9x23 ammunition all represent full-power loads. But handloads can bring out the full potential of this cartridge. Hodgdon and Vihtavuori offer load data. The current Hodgdon data is limited to one powder (Winchester 231) with limited performance (maximum of 1300 fps with a 125-grain JHP). However, Winchester's old 15th Edition Reloader's Manual also has data for Winchester Action Pistol (WAP) gunpowder. WAP was discontinued, but revived as Ramshot Silhouette. The Vihtavuori data is more expansive (three gunpowders, four bullets), but published velocities fall short of Winchester's factory loads.


Published data for both Winchester powders and Vihtavuori 3N37 was tested in Winchester 9x23 brass with the maximum charge weights given for these gunpowders. Winchester lists the pressures for both the 231 and WAP loads as 46,000 psi. The 231 and 3N37 powders came up short velocity-wise to their published values, but Silhouette did not disappoint.


Hornady makes dies for the 9x23, but not everyone does and those companies usually recommend using 9mm Luger dies, which is what I did. Only the sizing die would need to be different, and it's not very different because the dimensions are so similar.

A. Sectioned brass. Black arrows show the apprx. location of the Nowlin barrel's feed ramp and where cases were measured for wall thickness. B. Win. and Starline cases loaded with the same charge of Silhouette. Red arrow shows the imprint of the feed ramp.

Starline Brass

The Winchester brass is king. Its thick wall handles the pressure with ease in an unsupported chamber. Starline's 9x23 Comp brass is not as thick-walled as the Winchester brass (pictured). The Starline brass measured 0.034" thick whereas the Winchester wall measured 0.047" thick at a point 0.270" up from the base (illustrated with black arrows).

This raises the question of whether the Starline brass will hold up to the same pressure as the Winchester brass in an unsupported chamber. It does not. When loaded with the same high pressure charge of Silhouette, the Starline brass showed excess bulging in the unsupported region resulting in a large imprint of the feed ramp in the brass (footnote 2), the same as seen with the COR-BON ammunition. The Winchester brass did not bulge excessively or had at most a "microscopic" feed ramp imprint that could be seen under high magnification.

Thus there is a risk of case blowout with the Starline cases at 9x23-like pressure in an unsupported chamber and must be downloaded to ensure safety. (Note: this applies to the specific brass in my possession. A different lot of Starline 9x23 Comp might manage high pressure better or worse; Testing is required.) Brass with the imprint should be discarded because it is likely weakened there and could fail if reloaded and exposed to high pressure again.

Case Capacity

The Winchester brass' thicker wall means it has less case capacity than the Starline brass (Figure A below). Less room means more pressure with the same gunpowder charge. This difference was apparent in terms of velocity and pressure signs in the primers. The Winchester brass showed higher velocity with the same gunpowder charge and more primer flow (Figure B below).

Because the 9x23 operates at such high pressures, pistol primers are pushed to their limits — or beyond. I see primer flow in every round of factory Winchester 9x23 ammunition I fire in my pistol, I've even experienced a few pierced primers, and therefore I use rifle primers for handloads because they are designed to handle higher pressures.

A. The same charge weight of gunpowder in both cases shows that the Starline 9X23 Comp brass is filled to the brim, but the Winchester brass is overflowing. B. Primer flow (cratering) is greater in the Winchester brass. Both are Federal small rifle primers (No. 205). Same cases as in Figure 5B.

Maximizing performance in Starline brass; Lower pressure gunpowder?

Silhouette can duplicate the factory Winchester loading, but it produces a lot of pressure in the process, and the Starline 9x23 Comp brass bulges dangerously at this pressure in an unsupported chamber. I tried different load weights of Silhouette to determine the charge weight at which it would not excessively bulge the Starline 9x23 brass. It had to be downloaded to 6.6 grains of powder to be safe in my barrel which generated only 1168 fps. That falls well short of the 9x23's hallmark performance.

Will a different gunpowder provide better performance in the Starline brass? A general rule of thumb is that slower burning gunpowders will produce more velocity than faster burning gunpowders at the same pressure (footnote 3). Silhouette is considered a medium burning rate pistol powder. Other gunpowders were tested to see if they would produce higher velocities in the Starline cases without producing the excess bulge.

Hornady 124 grain FMJ FP bullets loaded to 1.245" COL. Federal small rifle primer.

This table (left) shows the gunpowders' highest charge weights and velocities achieved without producing excess bulging as indicated by the feed ramp imprint. Vihtavuori 3N38 showed the highest velocity at 1304 fps, which is 136 fps more than with Silhouette. The Starline 9x23 brass has limits in an unsupported chamber but selecting a different (usually slower) gunpowder can improve velocity while still maintaining a margin a safety.

Keep in mind if your 9x23 chamber offers full case support, then the Starline 9x23 brass will work fine for high pressure loads.

147-grain bullets are shown: a Remington FMJ FP with a square base and a Hornady XTP with a boat tail. The Rem. slightly bulged the Win. cases, as shown by arrows and a change in the shadow. The boat-tail bullet produced no bulge. Bullets were seated to 1.245" COL.

Heavy Bullets

Another difference between these two brass is how they fit heavier bullets. The Winchester's thicker case walls extend quite a distance up the side. This poses no problems for bullets up to 125 grains, but heavier bullets extend deeper in the case body. The Winchester brass' thick walls bulge slightly with square-based 147-grain bullets, whereas the Starline's case walls are designed to accommodate them. The bulge was about .005" wider than the non-bulged case at that location. The round still fit in the Nowlin chamber, but it did not readily slide in when the chamber was slightly dirty, indicating that it was a close fit. A boat-tailed 147-grain bullet produced no measurable bulge in the Winchester brass.

Load data

Load data for the 9X23 Winchester is limited. Some user-supplied load data can be found at Dane Burns' website. Savvy reloaders will also look at .38 Super and .38 Super Lapua data. This data is ideal for .38 Super brass, but don't forget that the Winchester 9x23 brass has less internal volume, which means higher pressure for the same powder charge, so load development based on .38 Super data requires adjustment and must be reduced if used in Winchester 9x23 cases. In all circumstances, start at the low end and work up watching for pressure signs.

The Other 9X23s

9X23_cartridgesThe 9X23 Winchester should not be confused with other 9x23 cartridges such as the 9mm Largo, (aka 9X23 Largo, 9mm Bayard Long, 9mm Bergmann-Bayard) and 9mm Steyr (aka 9X23mm Steyr). The Largo is also a tapered case but is slightly longer (0.910"), and it has a longer maximum COL as well (1.320"). The Steyr is a straight-walled round, like the .38 Super, with same-length brass but a longer maximum 1.300" COL. The Winchester 9x23 should never be fired in guns chambered for these other cartridges because 9x23 Winchester pressures far exceed these other rounds.


The 9x23 Winchester is a very powerful cartridge with impressive ballistics due to its high operating pressure. The Winchester factory ammunition provides high performance and durable brass for use in unsupported chambers. But ammunition choice is very limited, making handloading an appealing option.

Starline's 9x23 Comp brass proved to be much less durable in the unsupported Nowlin chamber, showing excess, dangerous bulging at caliber-typical pressure. Judicious handloading was required for this brass to be safe. Gunpowder selection could enhance ballistic performance with the Starline brass, but it could not match the full potential of original Winchester brass with the gunpowders tested.


Shooting Times nor the author are responsible for mishaps of any kind, which might occur from the use of factory or handloaded ammunition. It is the user's responsibility to follow safe shooting guidelines and to develop safe handloads.


Footnote 1. Dane Burns had noted in a forum thread that he experienced consistent case blowouts with COR-BON ammunition loaded in Starline 9x23 Comp cases. He also noted that as of 9/18/2009 all COR-BON 9x23 ammunition would be produced with Winchester brass. But this does not seem to be the current state. As per my email correspondence with COR-BON on 7-9-2013, they load their 9x23 ammunition exclusively in Starline brass unless they can find some NOS (New Old Stock) Winchester brass.  My sample of COR-BON 9x23 ammunition was several years old - unknown date of manufacture.

Footnote 2. Measurements showed that the feed ramp imprint appeared when the case wall at that location had expanded to 0.390" or greater for this barrel. Cases that were expanded to 0.387-0.389" showed no evidence of the feed ramp imprint. One of the Starline 9x23 Comp cases tested with a high pressure charge of Silhouette had expanded to .4005" in the unsupported region. Yikes!

Footnote 3. I have no way to measure pressure. There is an assumption that the brass' expansion is correlated with chamber pressure levels, but it might also be correlated with the shape of the pressure curve which differs between fast and slow burning gunpowders.  In either case, this test will compare case expansion with different gunpowders. Note: different burn rate charts place gunpowders in different positions.


ANSI/SAAMI booklet Z299.3-1993. American National Standard. Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Pistol and Revolver Ammunition for the Use of Commercial Manufacturers. 1993. Sporting Arms & Ammunition Manufacturers' Institute, Inc., Wilton, Conn. USA.

Brown, E. (1998) 9x23 in "Condition White", American Handgunner, September/October, pp. 55-56.

Cartridges of the World (2006) 11th Edition, by Frank C. Barnes, Edited by Stan Skinner. Gun Digest Books, Iola, WI.

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