The 9x25mm Dillon Cartridge

by Jeff Quinn

photography by Jeff Quinn & Boge Quinn

August 15th, 2012




Click pictures for a larger version.



The 9x25mm Dillon cartridge.



Lone Wolf conversion barrels.



DPM recoil-reducing guide rod system.



9x25mm Dillon cartridge (right) compared to parent 10mm cartridge (left).



Left to right; 357 Magnum, 357 Sig, 9x25 Dillon, 10mm Auto.

The 9x25mm Dillon cartridge has been around for about a quarter century. The cartridge was developed for competition use, and is simply the 10mm Auto case necked down to accept a 9mm bullet. The 9x25 is to the 10mm as the 357 Sig is to the 40 S&W. The latter case is a shorter version of the original 10mm, and both the 40 S&W and the 357 Sig are more popular today than their 10mm predecessor.

With manufacturers of firearms introducing more powerful revolver cartridges in recent years, and the shooting public’s acceptance of these new cartridges, it would seem that shooters of auto-pistols would welcome more power as well, but that does not seem to be the case, if firearm sales are an indicator. The popular 500 and 460 S&W magnums, the 500 Wyoming Express, 454 Casull, 475 & 500 Linebaugh, and other powerful revolver cartridges are more popular now than ever, but when it comes to cartridges for auto-pistols, the buyers are just not flocking towards the excellent 10mm, nor its offspring, the 9x25 Dillon.

High-performance ammunition is readily available for both cartridges. You are not going to run down to Wal-Mart and buy a box of 9x25, nor even a box of 10mm, but excellent ammunition is available online. I have written about the 10mm a few times before, so here we are looking at the 9x25 Dillon, and the advantages that the cartridge has over is weaker competitors.

One disadvantage that presents itself to most shooters is that the 9x25 is not currently chambered in any production pistol that is available off the shelf at your local gun dealer. While most well-stocked gun stores have plenty of 40 S&W and 357 Sig pistols available, the 10mm pistols will be scarce, and the 9x25 pretty much unavailable. However, converting a 10mm pistol to 9x25 Dillon is as easy as swapping the barrel. Lone Wolf Distributors has 9x25 Dillon barrels in stock and ready to ship for a simple swap in a 10mm Glock pistol. For 1911 users, Bar-Sto can supply a 9x25 Dillon barrel. The 9x25mm uses standard 10mm magazines, slides, extractors, and other parts, so the barrel is all that is needed to make the switch.

The 9x25 Dillon offers a significant velocity advantage over the 357 Sig, and gives 357 magnum performance out of a high-capacity auto-pistol. My favorite pistol for the conversion is a Glock Model 20SF. The Model 20SF is a reliable and affordable 10mm pistol, and the barrels for the conversion are easy to get and relatively inexpensive. Lone Wolf has barrels available in standard and extended lengths, and they also have a long slide available, for those who do not want an extended barrel protruding from the front of the slide.

The 9x25mm is a cartridge which, like most others, benefits from a longer-than-standard barrel length. The cartridge was developed to provide a fast-shooting cartridge to work well in compensated auto-pistols for ISPC competition, and in that role, it achieved its goal. However, it is not necessary to use the 9x25 to make major power in ISPC, and for that role, there are other cartridges which do just as well. I like the 9x25 for its flat-shooting power for use as a hunting and fighting pistol, and those is the applications which we will look at here.

The 357 magnum cartridge is well-established as a fight stopper and as a cartridge for taking whitetail deer and hogs. The 9x25 pushes a bullet that is very close to the diameter of the 357 magnum at the same nominal speeds, so the performance would be expected to be the same. For hunting, I prefer the lead-free hollowpoint bullets that are available from Barnes as the XPB, or one of the tougher hollowpoint cup-and-core bullets. For social work, these same bullets are great choices. Most any of the expanding bullets loaded commercially by Double Tap or by Underwood would be good choices for social work, but I prefer the heavier weights for deer and especially for hogs.

I fired every type of commercially-loaded ammunition for the 9x25 Dillon that I could find, to check velocities from two Lone Wolf barrels; one a six-inch non-ported barrel, and the other a five and one-half inch ported. Velocities were checked at a distance of twelve feet from the muzzle. Temperature at the range during testing hovered around the eighty-two degree Fahrenheit mark. Humidity was eighty-five percent. Range elevation was approximately 541 feet above sea level. FMJ is a full-metal-jacket bullet. JHP is a jacketed hollowpoint. HC is a hard-cast lead bullet. CE is a controlled expansion jacketed bullet. Velocities are listed in feet-per-second (FPS). Bullet weights are listed in grains.

Ammunition Bullet Weight Velocity 6.02" Velocity 5.47" Ported
Double Tap FMJ 95 1937 1853
Double Tap CE 95 1945 1866
Double Tap FMJ 125 1611 1540
Double Tap JHP 125 1597 1550
Double Tap FMJ 147 1301 1261
Double Tap HC 180 1212 1153
Underwood JHP 125 1670 1619
Underwood FMJ 125 1698 1635

The velocities recorded were rather impressive, besting velocities from a 357 Sig by a significant margin. The 357 Sig is a dandy cartridge, but the 9x25 does everything that the 357 Sig does, and shoots flatter and hits harder. Velocities from the ported barrel show a marked decrease under the velocities of the six inch. The 5.47 inch ported barrel is effectively closer to a five inch, as the ported section adds no velocity. Also, the ported barrel had a much greater amount of muzzle flash from the shooter’s viewpoint, and for that reason, I do not like a ported barrel on a fighting pistol, as after the first shot in low light, the shooter is effectively temporarily blinded by the muzzle flash. The six inch barrel shown will work equally well in a standard or long slide, and is the best choice for a hunting barrel for the 9x25. For carry, I would get a standard 4.6 inch barrel length, and the results should be close in velocity to those of the 5.47 inch ported, without the muzzle flash. Accuracy was very good, with both barrels being capable of turning in match-grade performance from a distance of twenty-five yards, secured into a Ransom Master Series machine rest.

The justification for the existence of the 9x25mm Dillon as a defensive and hunting cartridge must be in how it compares to its competition, being mainly the 357 magnum revolver cartridge, and the 357 Sig and 10mm auto-pistol cartridges. As a hunting cartridge, the 9x25 has no advantage over the 357 magnum revolver, as its greater capacity of cartridges in the firearm is not a very important factor, at least in whitetail hunting. If caught on the ground among a group of wild hogs, the extra rounds might be needed, but in most cases, they would not. In a gunfight, having sixteen rounds available without reloading as opposed to only six or seven could be very important. Compared to the 357 Sig cartridge, the 9x25mm is superior in both hunting and fighting situations, as it is basically the same bullet, moving faster, offering better penetration and higher impact velocities, with the proper bullet choice. Recoil is a bit more than that of the 357 Sig, but not enough to matter, in my opinion, and the weapon is much more controllable than a 357 magnum revolver of equal weight. The 9x25mm Dillon is easy to handle in the Glock 20 platform.

Compared to the 10mm Auto cartridge, which is better is a hard call. The weapon is identical in both handling, size, capacity, and weight, so it comes down to the performance of the two cartridges. The 10mm has a larger diameter bullet, and is capable of using bullets of heavier weight. On a whitetail deer, the difference is negligible, but for protection against a brown bear or a large hog, I prefer to have the 10mm in my hands. The 9x25mm shoots a bit flatter in trajectory, but again, the difference is negligible in a hunting situation. Same thing goes for a fighting gun; the 10mm throws a bigger bullet, so it again gets the nod.

The existence of the 9x25mm pretty much lies with its original intent as a competition gun, when compared to the other cartridges that were available at the time. With IPSC lowering its major caliber power factor, there are other cartridges which make the grade, with higher magazine capacity. As a high performance auto for hunting and defense, the 9x25 is an excellent choice, but arguably not as good as its parent, the 10mm. Still, it is an excellent cartridge, and I am glad to see it has a small but loyal following, just as does the 10mm. I think that both cartridges deserve greater popularity among shooters who are looking for more power from their handguns, and the 9x25 is at the top of the heap for auto pistol cartridges that provide high velocity, excellent accuracy, and good terminal performance in a medium-bore cartridge.

To order Lone Wolf conversion barrels, go to

To order 9x25 Dillon ammunition, go to and

Jeff Quinn

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Click pictures for a larger version.





Lone Wolf Long Slide with 6.02- inch barrel.





Ammo tested.