Peterson .257 Weatherby Magnum Brass Cases – 50 pcs

Peterson .257 Weatherby Magnum brass is a premium handloading component intended for shooters who require excellent dimensional consistency, uniform internal capacity and repeatable neck tension. Peterson introduced factory-made brass in this calibre in 2025, providing handloaders with a durable and consistent alternative to the previously available .257 Weatherby cases.

The .257 Weatherby Magnum was developed by Roy Weatherby in 1944 and commercially introduced in 1945. It is known for its extremely flat trajectory, high velocity and effectiveness in long-range hunting applications. Its characteristic belted case and double-radius Weatherby shoulder require particularly precise dimensional control during production.

Peterson manufactures its cases in the USA from C260 cartridge brass. The multi-stage production process includes several drawing operations, forming the case head and primer pocket, machining the extractor groove, precision forming of the body and shoulder, trimming, punching the flash hole and final induction annealing of the neck and shoulder.

Induction annealing allows the temperature applied to each case to be precisely controlled. This helps produce uniform material properties, consistent neck tension and repeatable bullet release. Peterson manufactures its brass in small production batches and inspects every finished case.

The .257 Weatherby Magnum version features a Large Rifle Primer pocket. Large Rifle Magnum primers are frequently used when loading this calibre, but the correct primer type should always be selected according to current published load data for the specific propellant and bullet combination.

Peterson brass users most frequently mention its durability, low case-weight variation, uniform neck-wall thickness and tight primer pockets. Reports concerning Peterson Weatherby-calibre brass also mention reduced case stretching and a greater number of possible reloading cycles compared with some Weatherby or Norma cases. Actual case life will always depend on pressure, the dimensions of the rifle chamber and the case-preparation procedure.

KEY ADVANTAGES

• factory-made .257 Weatherby Magnum brass,
• Match-Grade quality,
• Large Rifle Primer pocket,
• standard 0.080" / approximately 2.03 mm flash hole,
• manufactured from C260 cartridge brass,
• consistent internal case capacity,
• uniform body and neck-wall thickness,
• tight and precisely formed primer pockets,
• characteristic Weatherby shoulder formed to tight tolerances,
• induction-annealed neck and shoulder,
• precisely trimmed case mouth,
• designed for repeated reloading,
• manufactured in small production batches,
• every finished case inspected,
• manufactured in the USA,
• factory package containing 50 cases.

TECHNICAL SPECIFICATIONS

Manufacturer: Peterson Cartridge
Calibre: .257 Weatherby Magnum
Abbreviated designation: .257 Wby Mag
Product type: new rifle brass cases
Condition: new and unfired
Material: C260 cartridge brass
Case type: belted, bottleneck magnum
Shoulder design: characteristic Weatherby double-radius shoulder
Primer pocket: Large Rifle Primer
Flash-hole diameter: 0.080" / approximately 2.03 mm
Primers included: no
Neck and shoulder treatment: induction annealed
Finish: cleaned brass
Quantity: 50 cases
Country of manufacture: USA
Manufacturer number: 40063-R / 40063R
UPC/EAN: 810068270266

.257 WEATHERBY MAGNUM STANDARD DIMENSIONS

Maximum case length: 2.549" / 64.74 mm
Minimum cartridge overall length: 3.049" / 77.44 mm
Maximum cartridge overall length: 3.209" / 81.51 mm
Maximum case-head diameter: 0.5315" / 13.50 mm
Belt diameter: 0.532" / 13.51 mm
Case-body diameter above the belt: 0.5117" / approximately 13.00 mm
Case-body diameter near the shoulder: approximately 0.492" / 12.50 mm
Outside neck diameter: approximately 0.285" / 7.24 mm
Bullet diameter: 0.257" / approximately 6.53 mm
Belt height: 0.250" / 6.35 mm

Cartridge overall length is a specification for complete ammunition and not for the empty case itself.

PETERSON REFERENCE DATA – LOT K168

Average empty case weight: 234.2 gr / approximately 15.18 g
Average internal capacity: 81.0 gr H₂O / approximately 5.25 cm³
Shoulder diameter: 0.486" / approximately 12.34 mm
Base diameter: 0.510" / approximately 12.95 mm
Neck-wall thickness: 0.0128" / approximately 0.325 mm
Loaded neck diameter: 0.283" / approximately 7.19 mm
AMP Aztec code for lot K168: 0132
AMP pilot: #B15

For the second published lot, K168B, Peterson lists an average case weight of 234.5 gr, an internal capacity of 81.0 gr H₂O, a neck-wall thickness of 0.0125" and an AMP code of 0133. These results demonstrate very similar specifications between the two production lots.

The listed weight, capacity and dimensional values are reference measurements for specific production lots. Measurements may vary slightly between batches.

IMPORTANT INFORMATION

The internal capacity of Peterson brass may differ from Weatherby, Norma, Hornady or other manufacturers’ cases. A previously developed load should not be transferred without restarting load development from safe published starting data.

This also applies when changing from cases formed from .270 Weatherby Magnum brass to factory-made Peterson .257 Weatherby Magnum cases. Differences in case weight, internal capacity and wall thickness may affect pressure and velocity.

Every case should be inspected, measured and prepared before use according to your standard case-preparation procedure and the current instructions provided by the component manufacturers. Never exceed the maximum pressures specified by SAAMI or C.I.P.

FAQ

Are these factory-made .257 Weatherby Magnum cases?

Yes. The cases feature the correct .257 Weatherby Magnum headstamp and do not require forming from .270 Weatherby Magnum brass.

Do the cases include primers?

No. These are new, unprimed and unloaded brass cases.

What primer size do they require?

The cases have a Large Rifle primer pocket. Large Rifle Magnum primers are frequently used in the .257 Weatherby Magnum, but primer selection must follow current published load data.

Are the cases annealed?

Yes. The neck and shoulder are factory induction annealed. Visible discoloration in this area is a normal result of the annealing process and is not a product defect.

Is Peterson brass more durable than Weatherby or Norma brass?

Users frequently describe Peterson brass as stronger, less prone to stretching and better at retaining tight primer pockets. However, a specific number of reloading cycles cannot be guaranteed because case life depends on pressure, chamber dimensions and the case-preparation and annealing process.

Can I use a load previously developed with another brand of brass?

A finished load should not be transferred automatically. Because internal case capacity may differ, load development should be repeated using safe starting data from a current and reputable source.