Mec Mayville Progressive Shotshell Reloader For 20 Gauge. The Mec 20 Gauge Progressive Reloader features automatic indexing and shell ejection preset by the factory. Shells pass through each stage every time the handle is returned to the up position. E-Z Prime primer feeder included. Specifications for Mec Mayville Progressive Shotshell Reloader For 20 Gauge: Supplier SKU: 45309 Category: RELOADING PRESSES Type: Shotshell Reloading Press Material: Cast Iron Thread Size: N/A The Mec Mayville Progressive Shotshell Reloader For 20 Gauge is a quality addition to the MEC lineup. For more great deals on Reloading Presses by MEC please browse our Mec Reloading Equipment page.