The L.E. Wilson .33 cal .337" expanding mandrel is a precision neck-sizing tool for reloaders who demand consistency in their handloads. This mandrel works within Wilson's expanding mandrel die system to prepare new brass cases for bullet seating. New brass straight from the box often arrives with inconsistent neck dimensions—a legacy of bulk shipping and handling. Running cases over this mandrel brings neck diameter into spec before you seat bullets, which translates to tighter neck tension and more uniform seating depth from round to round.
The .337" mandrel is caliber-specific and sized for .33 caliber applications. It expands case necks to slightly under bullet diameter, creating the controlled fit that serious reloaders rely on for repeatable ballistics. The mandrel pairs with Wilson's standard 7/8" press die (sold separately) and features stainless construction for long-term durability. Wilson's reputation in precision reloading gear carries through in the engineering here—every dimension is held tight, from the mandrel taper to the included lock nut (.225" thickness, .270" height, 1.250" OD).
If you're already running a Wilson expanding mandrel die system or considering adding one to your bench, this replacement or additional mandrel gives you flexibility to work multiple calibers without buying a whole new die setup. Swap mandrels as your current projects demand. The cutout design in the die housing lets you visually confirm case alignment during setup, reducing trial-and-error on depth adjustment.
Key Features
- Stainless construction resists corrosion and wear
- Expands neck to slightly under bullet diameter for consistent fit
- Interchangeable design—use with Wilson expanding mandrel die system
- Precision-engineered lock nut for secure, repeatable depth setting
- Caliber-specific .337" size for .33 caliber cartridges
Specifications
| Brand | L.E. Wilson |
| Product Type | Expanding Mandrel (Neck Sizing) |
| Caliber | .33 cal |
| Mandrel Diameter | .337" |
| Press Die Size | Standard 7/8" reloading press |
| Material | Stainless Steel |
| Lock Nut Thickness | .225" |
| Lock Nut Height | .270" |
| Lock Nut Width (OD) | 1.250" |
Frequently Asked Questions
Is this mandrel compatible with my reloading press?
This mandrel is designed to work with Wilson's expanding mandrel die and standard 7/8" reloading press dies. The mandrel itself screws into the Wilson expanding mandrel die body (die sold separately). It will work with any standard reloading press that accepts 7/8" dies.
Can I use this mandrel for other calibers?
No. This mandrel is caliber-specific and sized for .33 caliber cartridges only. The .337" diameter is matched to .33 cal applications. L.E. Wilson makes mandrels for other calibers sold separately.
What's included with this purchase?
You receive the expanding mandrel only. The Wilson expanding mandrel die body (which holds the mandrel in your press) is sold separately. The lock nut is included as part of the mandrel assembly.
Why would I need multiple mandrels?
If you reload multiple calibers, buying mandrels for each caliber lets you swap them into a single die body rather than purchasing complete die sets for each caliber. This is a cost-effective way to expand your reloading setup across different cartridges.
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