||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (September 2014)|
|Place of origin||United States|
|Parent case||10mm Auto|
|Case type||Rimless, bottleneck|
|Bullet diameter||.356 in (9.0 mm)|
|Neck diameter||.380 in (9.7 mm)|
|Shoulder diameter||.423 in (10.7 mm)|
|Base diameter||.425 in (10.8 mm)|
|Rim diameter||.425 in (10.8 mm)|
|Rim thickness||.0550 in (1.40 mm)|
|Case length||.990 in (25.1 mm)|
|Overall length||1.250 in (31.8 mm)|
|Case capacity||24.9 gr H2O (1.61 cm3)|
|Rifling twist||1 in 16" (406 mm)|
|Primer type||Center-fire large pistol|
|Maximum pressure||36,259 psi (250.00 MPa)|
|Test barrel length: 6" (Lone Wolf SS 1:16" twist)
Source(s): DoubleTap Ammunition products page
Around 1987, Randy Shelley, an employee of Dillon Precision, necked down 10mm auto brass to 9mm. His goal was to get as much slow-burning powder in the case as possible in order to drive a 9mm bullet to the velocity needed to qualify for the IPSC Major power factor. The short-necked and steep-shouldered cartridge holds twice the powder of a .38 Super Auto case.
The 9×25mm Dillon was used by several notable IPSC shooters, such as Rob Leatham and Jack Barnes. Leatham developed loads with less blast and shock to mitigate this, but discovered there was little advantage over a similar load in .38 Super.
Most shooters, looking at the 9X25 Dillon today, focus on the extreme velocities it is capable of. A 115 grain bullet at 1800 fps is impressive, but more than needed for competition. There, a 115 only needed to be going a bit over 1500 fps to make Major. What competitors in the late 1980s and early 1990s who were using the 9X25 were doing was adjusting the powder used, to produce more pressure in the compensator, or muzzle brake. A muzzle brake works by diverting gases to reduce felt recoil. the greater the gas volume, or the pressure that gas is at, the more force the comp or brake creates. Competitors could "feed" the comp more gases. This turned out to be too much of a good thing. The muzzle blast created by the combination proved to be tiring over the course of a match. And the resulting recoil re-direction proved hard on elbows and shoulders.
What finally put an end to the 9X25 Dillon in competition were two things: barrel wear and magazine capacity. Barrels in high-pressure cartridges like .38 Super at Major velocities have a much shorter service life than lower-pressure ones. The 9X25 Dillon proved difficult to get through a competition season with the original barrel. Also, for any given length magazine (and magazine lengths were and are limited in USPSA/IPSC competition) a .38 Super will hold more rounds than a 9X25 will. This, as much as any reason, put an end to the short life of the 9X25 in competition.
9×25mm Dillon maximum cartridge dimensions. All sizes in millimeters (mm).
Americans would define the shoulder angle at alpha/2 = 30 degrees. The common rifling twist rate for this cartridge is 406 mm (1 in 16 in), 6 grooves, Ø lands = 8.79 mm, Ø grooves = 9.02 mm, land width = 3.07 mm and the primer type is large pistol.
According to the QuickLOAD database the 9x25mm Dillon case can handle up to 250 MPa (36,259 psi) piezo pressure. Since there are no C.I.P. or SAAMI limits and data sets for wildcat cartridges this data has to be regarded with caution.
The Austrian 9×25mm Super Auto G pistol cartridge is probably the closest ballistic twin of the 9×25mm Dillon. These cartridges are both necked down 9 mm variants of the 10 mm Auto cartridge though they dimensionally vary.
Making the 9×25mm Dillon is fairly easy. Dillon Precision makes the necessary resizing die and reliable reloading data is easily found. Most people were using 115 grain bullets, but bullets with weights as low as 80 grains were used too.
Loaded cartridges: As of 2015, DoubleTap offers several 9×25mm Dillon factory ammunition loads. As of December 2013, Underwood Ammo offers two loads in 9×25mm Dillon.
Conversions: Drop-in barrels are available as aftermarket parts for the Glock 20 and Glock 29 semi-automatic pistols. These pistols are originally chambered by Glock for parent cartridge of the 9×25mm Dillon, the 10mm Auto.
- 9x25 home page, October 7, 2001 archive accessed
- 9x25mm Dillon - 2nd Edition Lyman Pistol and Revolver Handbook, Page 91