.17 Mach IV
Left to right: .17 HMR, .17 Mach IV, .243 Win
Type Rifle
Place of origin United States
Production history
Designer Vern O Brien
Designed 1962
Parent case .221 Remington Fireball
Bullet diameter .172 in (Bad rounding hereScript error mm)
Neck diameter .206 in (Bad rounding hereScript error mm)
Shoulder diameter .361 in (Bad rounding hereScript error mm)
Base diameter .378 in (Bad rounding hereScript error mm)
Rim diameter .378 in (Bad rounding hereScript error mm)
Rim thickness .045 in (Bad rounding hereScript error mm)
Case length 1.400 in (Bad rounding hereScript error mm)
Rifling twist 1 in 10"
Primer type Small Rifle
Ballistic performance
Bullet weight/type Velocity Energy
25 gr (Bad rounding hereScript error g) HP3,680 ft/s (Bad rounding hereScript error m/s)797 ft·lbf (Bad rounding hereScript error J)
25 gr (Bad rounding hereScript error g) HP3,890 ft/s (Bad rounding hereScript error m/s)849 ft·lbf (Bad rounding hereScript error J)
Source(s): 6mmBR [1]

Hodgdon [1]

The .17 Mach IV is a wildcat centerfire rifle cartridge, based on the .221 Remington Fireball case, necked down to fire a .172 bullet. The cartridge was introduced in 1962 by Vern O’Brien.[2] The cartridge offered an easy case conversion and good ballistics, but could not compete against the .17 Remington.[3]

The name, Mach IV, comes from the claim that the bullets can reach 4,000 ft/s.[4] Due to the relatively small case capacity, even small variations in powder of 0.5 gr (Bad rounding hereScript error g) can lead to the difference between a safe and dangerously over pressure load.

The .17 Mach IV became very popular with varmint hunters, so much so that in 2007, Remington introduced its own very similar version, the .17 Remington Fireball.

See alsoEdit


  1. Hodgdon Online Reloading Data
  2. 6mmBR 17 Caliber Wildcats
  3. Barnes, Frank C., Cartridges of the World, 7th Edition, p171
  4. Which .17? by Jim Saubier

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