Pistol · Not SAAMI standardized · Not standardizedObsolete
13mm Gyrojet
13mm Gyrojet is a caseless straight-walled pistol cartridge of United States origin.
- Caliber
- 0.5094″ · 12.94 mm
- Introduced
- 1965
- Case
- Caseless
- Primary use
- Hunting, Self-Defense
- Status
- Discontinued
- Obsolete
- Obsolete
- Introduced
- 1965
- Type
- Pistol
- Origin
- United States
- Inventor
- Robert Mainhardt and Art Biehl (MBAssociates)
- Manufacturer
- MBAssociates
- Standard
- Not SAAMI standardized · Not standardized
- SAAMI
- Not SAAMI standardized
- Obsolete
- Obsolete
- Status
- Discontinued
- Availability
- Rare
- Twist (typical)
- 1:19.75
- Primer
- Small Pistol
- Case type
- Caseless
- Eff. range
- 50 yd
- Max range
- 250 yd
- Recoil
- 22.4–30.5 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for 13mm Gyrojet, 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
- —
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.
mixed/other · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 12.94 | 0.509 | · |
| Neck ⌀ | — | — | |
| Shoulder ⌀ | n/a | ||
| Shoulder angle | n/a | ||
| Base ⌀ | 12.94 | 0.509 | · |
| Rim ⌀ | 12.94 | 0.509 | ~ |
| Belt ⌀ | n/a | ||
| Rim thickness | — | — | |
| Neck length | n/a | ||
| Case length | 35.30 | 1.390 | · |
| Overall length | 35.30 | 1.390 | |
Missing a dimension for 13mm Gyrojet? Some case measurements aren't in a published SAAMI/CIP drawing yet. Have a factory or reamer print? Send it → — verified hard-to-find data earns a free Lindcott sticker.
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 13mm Gyrojet
Connected reference
History
Introduced around 1965 by Robert Mainhardt and Art Biehl (MBAssociates).
FAQs
- What twist rate does 13mm Gyrojet use?
- 13mm Gyrojet typically uses a 1:19.75 twist rate.
- What bullet diameter is 13mm Gyrojet?
- 13mm Gyrojet uses a 0.5094″ (12.94 mm) diameter bullet.
- Is 13mm Gyrojet still in production?
- 13mm Gyrojet is discontinued; typical availability is rare.
- What is 13mm Gyrojet used for?
- 13mm Gyrojet is primarily used for hunting, self-defense.
Sources & provenance
Data & sources. Specs compiled from the Lindcott Armory reference; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →
