Pistol · Not SAAMI standardized
.357 AutoMag
Pioneering semi-automatic pistol magnum cartridge, formed from cut-down .308 Winchester brass.
- Caliber
- 0.3591″ · 9.12 mm
- Introduced
- 1971
- Case
- Rimless
- Parent
- .44 AMP
- Primary use
- Hunting, Target
- Status
- Discontinued
- Introduced
- 1971
- Type
- Pistol
- Origin
- United States
- Inventor
- Harry Sanford / Auto Mag Corp
- Manufacturer
- Auto Mag Corporation
- Standard
- Not SAAMI standardized
- Status
- Discontinued
- Availability
- Collector
- Case capacity
- 35 gr H₂O
- Twist (typical)
- 1:18.75
- Primer
- Small Pistol Magnum
- Case type
- Rimless
- Max pressure
- 36,985 psi, CIP transducer
- Eff. range
- 100 yd
- Max range
- 2650 yd
- Recoil
- 8–9 ft·lb
- Subsonic
- Capable
Ballistics
Published velocity/energy data isn't available for .357 AutoMag — an obsolete/collector cartridge. Parent case: .44 AMP.
Performance
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
CIP TDCC · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 9.12 | 0.359 | ~ |
| Neck ⌀ | 9.75 | 0.384 | ✓ |
| Shoulder ⌀ | 11.71 | 0.461 | ✓ |
| Shoulder angle | 20° | — | ✓ |
| Base ⌀ | 11.97 | 0.471 | ✓ |
| Rim ⌀ | 12.01 | 0.473 | ✓ |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.37 | 0.054 | ✓ |
| Neck length | 6.17 | 0.243 | ≈ |
| Case length | 33.00 | 1.299 | ✓ |
| Overall length | 40.65 | 1.600 | ✓ |
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. .357 AutoMag is highlighted below.
Factory loads
Being verified
Advertised FPS, energy, and BC are withheld until loads clear verification.
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.
Firearms chambered in .357 AutoMag
Lineage
Necked down to .357
History
Developed in 1971 by Harry Sanford for the Auto Mag pistol — a gas-operated stainless steel semi-automatic using rifle-derived brass. The Auto Mag was designed to be the most powerful semi-automatic pistol available. The Auto Mag Corporation went bankrupt several times; the pistols were manufactured inconsistently and quality varied dramatically. Lee Jurras at Super Vel loaded the factory ammunition. Clint Eastwood used the Auto Mag in 'Sudden Impact' (1983), significantly raising its profile.
FAQs
- What twist rate does .357 AutoMag use?
- .357 AutoMag typically uses a 1:18.75 twist rate.
- What bullet diameter is .357 AutoMag?
- .357 AutoMag uses a 0.3591″ (9.12 mm) diameter bullet.
- Is .357 AutoMag still in production?
- .357 AutoMag is discontinued; typical availability is collector.
- What is .357 AutoMag used for?
- .357 AutoMag is primarily used for hunting, target.
- What is .357 AutoMag based on?
- .357 AutoMag is derived from the .44 AMP case.
Sources & provenance
- Standard C.I.P. — C.I.P. TDCC — Tables of Dimensions of Cartridges and Chambers
- Standard SAAMI — ANSI/SAAMI Z299 — Cartridge & Chamber Drawings archived
- Reference Gun Digest — Ammo Brief: .44 Auto Mag (Cartridges of the World excerpt) · parent_cartridge
- Secondary Wikipedia: .44 AMP (citing Donnelly, Handloader's Manual of Cartridge Conversions, 2011) · parent_cartridge
- Secondary Auto Mag Pistol — Wikipedia (.357 AMP is the .44 AMP necked down) · parent_cartridge
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 18 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →
