Rifle · SAAMI
.25 Weatherby RPM
Modern .257-caliber Weatherby RPM-family hunting cartridge..
- Caliber
- 0.257″ · 6.528 mm
- Introduced
- 2026
- Case
- Rebated
- Parent
- 6.5mm Weatherby RPM
- Primary use
- Hunting, Long range
- Status
- Active
- Introduced
- 2026
- Type
- Rifle
- Origin
- United States
- Inventor
- Weatherby
- Manufacturer
- Weatherby
- Standard
- SAAMI
- Status
- Active
- Availability
- Limited
- Primer
- Large Rifle Magnum
- Case type
- Rebated
- Max pressure
- 65,000 psi
- Eff. range
- 500 yd
Introduced by Weatherby
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for .25 Weatherby RPM, 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
- 6.5mm Weatherby RPM
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.
SAAMI · verified| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 6.53 | 0.257 | ✓ |
| Neck ⌀ | 7.37 | 0.290 | ✓ |
| Shoulder ⌀ | 12.10 | 0.476 | ✓ |
| Shoulder angle | 35° | — | ✓ |
| Base ⌀ | 12.70 | 0.500 | ✓ |
| Rim ⌀ | 12.01 | 0.473 | ✓ |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.37 | 0.054 | ✓ |
| Neck length | 7.07 | 0.278 | ≈ |
| Case length | 60.96 | 2.400 | ✓ |
| Overall length | 84.84 | 3.340 | ✓ |
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. .25 Weatherby RPM 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 for 2026 (SAAMI drawing Jan 2026); a shortened, necked-down 6.5 Wby RPM. MAP 65,000 psi. SAAMI reference load is 133gr @ 3,000 fps.
FAQs
- What bullet diameter is .25 Weatherby RPM?
- .25 Weatherby RPM uses a 0.257″ (6.528 mm) diameter bullet.
- Is .25 Weatherby RPM still in production?
- .25 Weatherby RPM is active; typical availability is limited.
- What is .25 Weatherby RPM used for?
- .25 Weatherby RPM is primarily used for hunting, long range.
- What is .25 Weatherby RPM based on?
- .25 Weatherby RPM is derived from the 6.5mm Weatherby RPM 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 →