#20a 20\ Shoulder (above 30 Caliber) Bump Gage Insert

The #20a 20" Shoulder (above 30 Caliber) Bump Gage Insert by Sinclair International is a precision reloading tool designed for handloaders and ammunition manufacturers who require absolute consistency in rifle cartridge production. This insert serves as a critical component within the larger bump gage assembly, enabling shooters to verify maximum cartridge overall length and shoulder positioning for calibers above .30.

Manufactured to tight tolerances, this gage insert functions as a mechanical go/no-go reference standard for large-magnum and belted rifle cartridges. The #20a designation specifically addresses larger-diameter shoulder designs found in magnum and specialized hunting rounds. Its precision-ground surfaces ensure consistent shoulder contact points, eliminating measurement variables introduced by worn or improvised alternatives.

Ideal for reloaders working with magnum cartridges such as .300 Win Mag, .338 Lapua, and .375 H&H, this insert directly impacts feeding reliability and case longevity. It integrates seamlessly into Sinclair's modular gage system, allowing users to swap caliber-specific inserts without replacing the entire assembly. This versatility makes it an essential tool for competitive benchrest shooters, law enforcement armorers, and military ammunition technicians.