Rifle · SAAMI
.257 Roberts
Classic quarter-bore beloved by riflemen.
- Caliber
- 0.257″ · 6.528 mm
- Introduced
- 1934
- Case
- Rimless
- Parent
- 7mm Mauser
- Primary use
- Hunting, Target
- Status
- Active
- Introduced
- 1934
- Type
- Rifle
- Origin
- United States
- Inventor
- Ned Roberts / A.O. Niedner
- Manufacturer
- Remington Arms
- Standard
- SAAMI
- Status
- Active
- Availability
- Moderate
- Case capacity
- 58 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Large Rifle
- Case type
- Rimless
- Max pressure
- 54,000 psi, SAAMI transducer
- Eff. range
- 300 yd
- Max range
- 4000 yd
- Recoil
- 12–14.3 ft·lb
This cartridge: 54,000 psi, SAAMI transducer
Introduced by Remington Arms
Ballistics
Published velocity/energy data isn't available for .257 Roberts. Parent case: 7mm Mauser.
Performance
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 ⌀ | 10.95 | 0.431 | ✓ |
| Shoulder angle | 20.8° | — | ✓ |
| Base ⌀ | 11.97 | 0.471 | ✓ |
| Rim ⌀ | 12.01 | 0.473 | ✓ |
| Belt ⌀ | n/a | ||
| 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 is highlighted below.
Factory loads
Being verified
Advertised FPS, energy, and BC are withheld until loads clear verification.
Suitable powders
1 reloading powder listed for .257 Roberts, fastest to slowest. Cross-reference in the finder →
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
Originated as wildcat in 1920s by Ned Roberts and A.O. Niedner, necking down 7x57 Mauser. Remington commercialized in 1934. Unfortunately, Remington used conservative loads due to weak surplus Mauser actions on market, neutering its performance. Proper handloads or +P ammunition show its true potential. Never achieved massive popularity but has devoted following. One of the most beloved wildcats-turned-commercial.
FAQs
- What twist rate does .257 Roberts use?
- .257 Roberts typically uses a 1:10 twist rate.
- What bullet diameter is .257 Roberts?
- .257 Roberts uses a 0.257″ (6.528 mm) diameter bullet.
- Is .257 Roberts still in production?
- .257 Roberts is active; typical availability is moderate.
- What is .257 Roberts used for?
- .257 Roberts is primarily used for hunting, target.
- What is .257 Roberts based on?
- .257 Roberts is derived from the 7mm Mauser case.
- What are the best powders for .257 Roberts?
- Reloading powders commonly listed for .257 Roberts include Reloader 17.
Sources & provenance
- Standard SAAMI — ANSI/SAAMI Z299.4-2025 — Centerfire Rifle Velocity & Pressure Data · grain_ballistics, representative_gun archived
- Standard SAAMI — ANSI/SAAMI Z299 — Cartridge & Chamber Drawings archived
- Manufacturer Winchester Ammunition — Power-Point rifle ammunition — 358 Winchester, symbol X3582 · representative_gun, grain_ballistics
- Manufacturer Hornady — 257 Roberts +P 117 gr SST Superformance (#81353) · grain_ballistics, representative_gun archived
- Manufacturer Federal Premium — Custom Shop Rifle Ammo — 257 Roberts +P 110 gr Nosler AccuBond (FCS257RAB1) · representative_gun, grain_ballistics
- Manufacturer Nosler — Trophy Grade Ammunition — 257 Roberts +P 110 gr AccuBond (60010) · grain_ballistics, representative_gun archived
- Manufacturer Remington — Core-Lokt 257 Roberts 117 Grain Soft Point (#28335) · grain_ballistics, representative_gun archived
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 31 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →
