A quick look at .17 Remington Fireball, another brainchild of P.O. Ackley.
One of many wildcats dreamed up by P.O. Ackley through the years was the .17/221 Fireball, which is the .221 Remington Fireball case necked down for bullets measuring .172-inch in diameter. When Las Vegas gunsmith Vern O’Brien started building custom rifles around the small Sako L461 action, he obtained permission from Ackley to chamber them for the .17/221 but decided to rename it the .17 Mach IV. O’Brien offered the same chambering in custom single-shot pistols built on the XP-100 action, but called it the .17 Mach III, due to lower velocities from their shorter barrels.
As is commonly seen in more than one wildcat, dimensions can vary slightly among makers of chamber reamers, which means that even though at first glance the .17 Remington Fireball appears to be the old .17 Mach IV with a different name, a closer inspection may reveal minor dimensional differences. For this reason, Remington discourages the firing of .17 Fireball ammunition in rifles chambered to .17 Mach IV and vice versa.
General Comments
Even though case dimensions of the .17 Fireball can differ a bit from those of the .17 Mach IV, the two cartridges are virtually identical in powder capacity and for this reason their velocity potential is the same. Capable of accelerating a 20-grain bullet along at over 4,000 fps, the trajectory of the .17 Fireball is quite flat, and mild recoil makes the little cartridge lots of fun to shoot.
Contrary to what has been written about the .17 Mach IV in the past and will likely be written about the .17 Fireball in the future, neither cartridge is capable of matching the velocities of the .17 Remington, which is on a modified version of the more capacious .223 Remington case. It has also been written that bullet jacket fouling builds up more rapidly in a rifle chambered for the .17 Remington, but the original author of Cartridges of the World found this to be untrue when the three cartridges are used in barrels having bores of equal quality and smoothness.
.17 Remington Fireball Loading Data and Factory Ballistics
| Bullet (grains/type) | Powder | Grains | Velocity | Energy | Source |
| 20 Hornady V-Max | H4198 | 17.3 | 4,037 | 722 | Hodgdon |
| 20 Hornady V-Max | H335 | 20.5 | 4,027 | 719 | Hodgdon |
| 25 Hornady HP | Benchmark | 19.0 | 3,745 | 778 | Hodgdon |
| 25 Hornady HP | IMR-4198 | 16.2 | 3,692 | 756 | Hodgdon |
| 30 Berger HP | H322 | 18.0 | 3,533 | 831 | Hodgdon |
| 30 Berger HP | Benchmark | 18.7 | 3,569 | 848 | Hodgdon |
| 20 AccuTip-V | FL | FL | 4,250 | 802 | Remington |
| 25 HP | FL | FL | 3,850 | 823 | Remington |
Editor's Note: This article is an excerpt of Gun Digest's Cartridge's Of The World.
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