Rifle · CIP
.255 GS
.255 GS is a rimless bottlenecked rifle cartridge of Italy origin.
- Caliber
- 0.2575″ · 6.54 mm
- Introduced
- 1980
- Case
- Rimless
- Parent
- 6.5x55mm Swedish
- Primary use
- Hunting
- Status
- Active
- Introduced
- 1980
- Type
- Rifle
- Origin
- Italy
- Inventor
- Vittorio Giani
- Manufacturer
- Vittorio Giani
- Standard
- CIP
- Status
- Active
- Availability
- Limited
- Case capacity
- 62 gr H₂O
- Twist (typical)
- 1:10.0
- Primer
- Large Rifle
- Case type
- Rimless
- Max pressure
- 63,817 psi, CIP transducer
- Eff. range
- 400 yd
- Max range
- 2000 yd
- Recoil
- 10.8–12.4 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for .255 GS, 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
- 6.5x55mm Swedish
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.
CIP TDCC · verified| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 6.54 | 0.257 | ✓ |
| Neck ⌀ | 7.38 | 0.291 | ✓ |
| Shoulder ⌀ | 11.58 | 0.456 | ✓ |
| Shoulder angle | 35° | — | ≈ |
| Base ⌀ | 12.20 | 0.480 | ✓ |
| Rim ⌀ | 12.20 | 0.480 | ✓ |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.50 | 0.059 | ✓ |
| Neck length | 7.94 | 0.313 | ≈ |
| Case length | 55.00 | 2.165 | ✓ |
| Overall length | 72.50 | 2.854 | ✓ |
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. .255 GS 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
Introduced around 2010.
FAQs
- What twist rate does .255 GS use?
- .255 GS typically uses a 1:10.0 twist rate.
- What bullet diameter is .255 GS?
- .255 GS uses a 0.2575″ (6.54 mm) diameter bullet.
- Is .255 GS still in production?
- .255 GS is active; typical availability is limited.
- What is .255 GS used for?
- .255 GS is primarily used for hunting.
- What is .255 GS based on?
- .255 GS is derived from the 6.5x55mm Swedish case.
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 →
