Rifle · Wildcat
.17 Mach IV
An early .17-caliber centerfire wildcat on a necked-down .221 Remington Fireball case, years ahead of factory rounds like the .17 Remington Fireball..
- Caliber
- 0.172″ · 4.369 mm
- Introduced
- 1963
- Case
- Rimless
- Parent
- .221 Remington Fireball
- Primary use
- Hunting
- Status
- Wildcat
- Introduced
- 1963
- Type
- Rifle
- Origin
- United States
- Inventor
- Vern O'Brien
- Manufacturer
- Handloaded only (wildcat; no factory ammunition)
- Standard
- Wildcat
- Status
- Wildcat
- Availability
- Rare
- Case capacity
- 21.9 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Small Rifle
- Case type
- Rimless
- Max pressure
- 48,000 psi, SAAMI transducer
- Eff. range
- 250 yd
- Max range
- 2800 yd
- Recoil
- 1.3–1.4 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for .17 Mach IV, so this is the shape gravity alone gives the advertised velocity. Drag would steepen it. The tool below solves real loads through their published G1 or G7 model.
Open in Ballistic Compare- Parent case
- .221 Remington Fireball
Representative trajectory — modeled from a single velocity input (no published BC for this cartridge yet).
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
reloading data · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 4.37 | 0.172 | · |
| Neck ⌀ | 5.23 | 0.206 | ~ |
| Shoulder ⌀ | 9.14 | 0.360 | · |
| Shoulder angle | 30° | — | · |
| Base ⌀ | 9.53 | 0.375 | · |
| Rim ⌀ | 9.60 | 0.378 | · |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.14 | 0.045 | · |
| Neck length | 5.16 | 0.203 | ≈ |
| Case length | 35.56 | 1.400 | · |
| Overall length | 44.96 | 1.770 | ~ |
Size vs familiar rounds
Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. .17 Mach IV is highlighted below.
Reloading costestimate cost per round vs factory
Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.
Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.
Lineage
Connected reference
History
The .17 Mach IV was introduced in 1963 by Vern O'Brien, based on the .221 Remington Fireball case.
FAQs
- What twist rate does .17 Mach IV use?
- .17 Mach IV typically uses a 1:10 twist rate.
- What bullet diameter is .17 Mach IV?
- .17 Mach IV uses a 0.172″ (4.369 mm) diameter bullet.
- Is .17 Mach IV still in production?
- .17 Mach IV is wildcat; typical availability is rare.
- What is .17 Mach IV used for?
- .17 Mach IV is primarily used for hunting.
- What is .17 Mach IV based on?
- .17 Mach IV is derived from the .221 Remington Fireball case.
Sources & provenance
- Manufacturer Hornady — Hornady Obsolete Load Data — 17 Mach IV · grain weights, bullet ⌀, velocity archived
- Secondary Wolfe Publishing — Rifle Magazine — The .17 Mach IV Cartridge · year, parent_cartridge, velocity archived
- Secondary .17 Mach IV — Wikipedia (pointer; cites O'Brien development) · parent_cartridge
Data & sources. Specs compiled from the Lindcott Armory reference; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →
