L.E. Wilson Die W/ Expanding Mandrel 33 - .337''

The L.E. Wilson expanding mandrel die in .337" is a precision reloading die built to standardize case neck diameter and tension before bullet seating. If you're working with new brass—especially after shipping and handling can crimp or dent necks—this tool restores uniformity and consistency across your entire batch. The expanding mandrel gently opens the case neck to just under your bullet's diameter, ensuring every round seats with the same tension and depth. That uniformity translates directly to tighter groups and more predictable ballistics downrange.

Built from stainless steel with a cut-out body design, the die lets you see exactly what's happening as you work—no guessing about case alignment or mandrel depth. It threads into any standard 7/8" reloading press, and L.E. Wilson includes a precision-machined lock nut (.225" inner height, .270" total height, 1.250" OD) to lock the die securely in place once you've dialed in your setup. The design accommodates interchangeable mandrels (sold separately) so you can expand different calibers with a single die body.

L.E. Wilson's reputation in the reloading world rests on American-made quality and attention to detail. This die is no exception—it's a workhorse for handloaders who understand that consistency in preparation pays dividends in accuracy and performance. Whether you're prepping once-fired brass or bringing new production cases up to standard, this expanding mandrel die removes a major source of variance from your reloading process.

Key Features

• Expands case neck to just under bullet diameter for uniform tension and seating depth
• Stainless steel construction for durability and corrosion resistance
• Cut-out die body provides clear visibility for alignment and depth adjustment
• Compatible with standard 7/8" reloading presses
• Includes precision L.E. Wilson lock nut for secure die positioning
• Accepts interchangeable mandrels (sold separately) for different calibers
• Ideal for conditioning new brass or restoring once-fired cases
• Made in the USA

Specifications

Frequently Asked Questions

What presses work with the L.E. Wilson expanding mandrel die?

This die is compatible with any standard 7/8" reloading press, which covers nearly all single-stage and most progressive machines in common use.

Can I use this die for different calibers?

Yes. The die body accepts interchangeable mandrels, so you can swap in mandrels for other calibers as needed. Mandrels are sold separately and sized to match your specific cartridge.

What comes in the box?

The die includes one .337" expanding mandrel and an L.E. Wilson lock nut. If you want to expand other calibers, additional mandrels are available separately.

Is this die useful for new brass, or just once-fired cases?

It's especially valuable for new brass. Factory-fresh cases often have inconsistent or damaged neck dimensions from bulk packaging. Running them through an expanding mandrel die brings them to a uniform standard before your first loading cycle, which improves consistency and accuracy.