The RCBS Neck Expander Body (brand part no. 39800) is a case-prep die from RCBS used when loading cast bullets into bottleneck rifle cases. It expands the neck of the case while simultaneously flaring the mouth slightly, combining two steps that would otherwise require separate operations. This one-step approach helps handloaders accurately seat cast bullets without shaving lead off the bullet’s surface, keeping bullet weight and balance consistent from round to round. RCBS sells expander body units in a range of diameters to match different cast-bullet calibers, sold separately.

Key Specifications

• Combines neck expansion and mouth flaring into a single reloading step.
• Purpose-built for cast bullet handloading in bottleneck rifle cases.
• Prevents lead shaving during bullet seating, preserving bullet weight and balance.
• Sold as part of a family of expander bodies covering several different diameters, each sold separately for the intended caliber.
• Weighs approximately 0.66 lb, a compact single-die accessory for the reloading bench.

Frequently Asked Questions

What does this expander body do? It expands the case neck and flares the mouth in one step, so a cast bullet can be seated without shaving lead.

Is this for jacketed or cast bullets? RCBS designs it specifically for cast bullets, where preventing lead shaving during seating matters most.

Does one expander body fit every caliber? No, RCBS offers expander bodies in several diameters sold separately, so handloaders select the one matching their cartridge.

Buy the RCBS Neck Expander Body

Order the RCBS Neck Expander Body from our reloading dies selection. Ships fast from our Lubbock, TX gun shop.