Pistol · Not SAAMI standardized · Not standardizedObsolete
8.5mm Mars
8.5mm Mars is a rimless bottlenecked pistol cartridge of United Kingdom origin.
- Caliber
- 0.3311″ · 8.41 mm
- Introduced
- 1899
- Case
- Rimless
- Primary use
- Self-Defense, Target
- Status
- Obsolete
- Obsolete
- Obsolete
- Introduced
- 1899
- Type
- Pistol
- Origin
- United Kingdom
- Inventor
- Hugh Gabbett-Fairfax
- Manufacturer
- Kynoch
- Standard
- Not SAAMI standardized · Not standardized
- SAAMI
- Not SAAMI standardized
- Obsolete
- Obsolete
- Status
- Obsolete
- Availability
- Collector
- Case capacity
- 21.1 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Small Pistol
- Case type
- Rimless
- Max pressure
- 14,500 psi, CIP transducer
- Eff. range
- 50 yd
- Max range
- 250 yd
- Recoil
- 11.4 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for 8.5mm Mars, 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.
Wikipedia · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 8.41 | 0.331 | · |
| Neck ⌀ | 9.10 | 0.358 | · |
| Shoulder ⌀ | 10.60 | 0.417 | · |
| Shoulder angle | 23° | — | |
| Base ⌀ | 10.70 | 0.421 | · |
| Rim ⌀ | 10.40 | 0.409 | · |
| Belt ⌀ | n/a | ||
| Rim thickness | 0.90 | 0.035 | · |
| Neck length | 4.39 | 0.173 | |
| Case length | 26.00 | 1.024 | · |
| Overall length | 36.80 | 1.449 | · |
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. 8.5mm Mars is highlighted below.
Missing a dimension for 8.5mm Mars? 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.
Connected reference
History
Introduced around 1899.
FAQs
- What twist rate does 8.5mm Mars use?
- 8.5mm Mars typically uses a 1:10 twist rate.
- What bullet diameter is 8.5mm Mars?
- 8.5mm Mars uses a 0.3311″ (8.41 mm) diameter bullet.
- Is 8.5mm Mars still in production?
- 8.5mm Mars is obsolete; typical availability is collector.
- What is 8.5mm Mars used for?
- 8.5mm Mars is primarily used for self-defense, target.
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 →
