9×25mm Dillon

Type

Pistol

Place of origin

United States

Production history

Designer

Dillon Precision

Designed

1988

Specifications

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

22.8 gr H₂O (1.48 cm³)

Rifling twist

1 in 16" (406 mm)

Primer type

Center-fire large pistol

Maximum pressure

36,259 psi (250.00 MPa)

Ballistic performance

Bullet mass/type	Velocity	Energy
90 gr (6 g) Gold Dot JHP	2,100 ft/s (640 m/s)	881 ft·lbf (1,194 J)
95 gr (6 g) FMJ	2,000 ft/s (610 m/s)	844 ft·lbf (1,144 J)
115 gr (7 g) Speer Gold Dot JHP	1,800 ft/s (550 m/s)	827 ft·lbf (1,121 J)
125 gr (8 g) FMJ-FP Match or Speer Gold Dot JHP	1,700 ft/s (520 m/s)	802 ft·lbf (1,087 J)
147 gr (10 g) FMJ-FP	1,495 ft/s (456 m/s)	730 ft·lbf (990 J)

Test barrel length: 6" (Lone Wolf SS 1:16" twist)
Source(s): DoubleTap Ammunition products page

The 9×25mm Dillon is a pistol wildcat cartridge developed for use in USPSA/IPSC Open guns. The cartridge is made by necking down a 10mm Auto case to 9 mm.

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 then IPSC Major power factor of 175. 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 9×25mm 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 9×25mm Dillon 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 9×25mm Dillon in competition was component wear, magazine capacity and lowering of the USPSA Major power factor from 175 to 165 (160 for IPSC competition). Barrels and compensators in high-pressure cartridges like .38 Super at Major velocities have a much shorter service life than lower-pressure ones. For maximum-permitted length magazines as used in USPSA/IPSC competition, a .38 Super magazine holds more rounds than a 9×25mm Dillon magazine. With the lowering of the USPSA power factor, safety and effectiveness of .38 Super loads improved to a point that the 9×25mm Dillon was no longer competitive and once worn out, pistols were often retired or rebuilt in .38 Super.

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Wikipedia