Rifle · SAAMI
.257 Roberts +P
SAAMI Active +P rifle cartridge (Z299.4).
- Caliber
- 0.257″ · 6.528 mm
- Introduced
- 1970
- Case
- Rimless
- Parent
- .257 Roberts
- Primary use
- Hunting, Target
- Status
- Active
- Introduced
- 1970
- Type
- Rifle
- Origin
- United States
- Inventor
- Ned Roberts / A.O. Niedner
- Manufacturer
- Remington Arms
- Standard
- SAAMI
- Status
- Active
- Availability
- Moderate
- Case capacity
- 55 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Large Rifle
- Case type
- Rimless
- Max pressure
- 58,000 psi, SAAMI transducer
- Eff. range
- 400 yd
- Max range
- 4550 yd
- Recoil
- 9.5–11 ft·lb
This cartridge: 58,000 psi, SAAMI transducer
Introduced by Remington Arms
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for .257 Roberts +P, 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
- .257 Roberts
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| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 6.53 | 0.257 | |
| Neck ⌀ | 7.37 | 0.290 | |
| Shoulder ⌀ | 10.95 | 0.431 | |
| Shoulder angle | 20.8° | — | |
| Base ⌀ | 11.97 | 0.471 | |
| Rim ⌀ | 12.01 | 0.473 | |
| Belt ⌀ | — | — | |
| Rim thickness | 1.24 | 0.049 | |
| Neck length | 8.16 | 0.321 | |
| Case length | 56.72 | 2.233 | |
| Overall length | 70.61 | 2.780 |
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. .257 Roberts +P 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.
Firearms chambered in .257 Roberts +P
Connected reference
History
The .257 Roberts +P was introduced in 1934 by Ned Roberts / A.O. Niedner, based on the .257 Roberts case (United States).
FAQs
- What twist rate does .257 Roberts +P use?
- .257 Roberts +P typically uses a 1:10 twist rate.
- What bullet diameter is .257 Roberts +P?
- .257 Roberts +P uses a 0.257″ (6.528 mm) diameter bullet.
- Is .257 Roberts +P still in production?
- .257 Roberts +P is active; typical availability is moderate.
- What is .257 Roberts +P used for?
- .257 Roberts +P is primarily used for hunting, target.
- What is .257 Roberts +P based on?
- .257 Roberts +P is derived from the .257 Roberts 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 →
