Weatherby Brass 338-378 Weatherby Magnum Ammunition - Box of 20 Rounds

The Weatherby Brass 338-378 Weatherby Magnum ammunition components are precision-engineered unprimed rifle brass cases designed for handloaders building ammunition for one of Weatherby's most powerful magnum cartridges. These 20-round boxes deliver CNC-machined primer pockets and strict grade specifications that serious reloaders depend on for consistent, reliable loads. Whether you're assembling factory-equivalent ammunition for long-range hunting or precision rifle work, starting with quality brass is the foundation of safe, accurate handloading.

Weatherby brass is a go-to choice among hunters and precision shooters who demand consistency shot after shot. The CNC-machined primer pockets ensure uniform ignition characteristics, which translates to tighter velocity spreads and better downrange performance. Because these are unprimed cases straight from the manufacturing process, you'll want to inspect, size, deburr, and chamber them before reloading—standard prep work that optimizes concentricity and case life. You may notice slight discoloration near the neck; this is a byproduct of the annealing process that actually improves the brass's expand-and-contract durability and bullet retention over multiple reload cycles.

If you're building 338-378 Weatherby Magnum loads for elk, moose, or long-range target work, these components give you a known starting point. Weatherby brass has earned its reputation in the reloader community for holding up through multiple firings and delivering the shot-to-shot uniformity that separates precision handloads from mediocre ones.

Key Features

• CNC-machined primer pockets for uniform ignition and consistency
• Strict grade specifications for reliable reloading performance
• Annealed for flexibility and secure bullet hold across multiple reload cycles
• 20 unprimed cases per box—ready for sizing, deburring, and loading

Specifications

Frequently Asked Questions

Do these cases come primed and ready to reload?

No, these are unprimed cases. You'll need to prime them yourself as part of your handloading process, along with standard case prep (sizing, deburring, and chamfering).

What's the stain or discoloration I might see near the neck?

That's a normal byproduct of the annealing process used during manufacturing. Annealing heats the brass to a specific temperature and cools it rapidly, which improves the material's flexibility and ensures it holds the bullet securely through multiple reload cycles.

Will I need to do case prep before loading?

Yes. The supplier notes that cases should be sized, deburred, and chamfered before reloading to ensure the mouth is perfectly round and ready for consistent bullet seating.

What is this brass used for?

The 338-378 Weatherby Magnum is a powerful long-range cartridge popular for hunting large game like elk and moose, and for precision rifle competition. These cases are for handloaders building ammunition for those applications.