#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 engineered for handloaders and ammunition manufacturers who demand absolute consistency in rifle cartridge production. This insert functions as a critical component within the larger bump gage assembly, allowing shooters to verify maximum cartridge overall length and shoulder positioning for calibers above .30. Whether you're a competitive benchrest shooter, law enforcement armorer, or military ammunition technician, this gage insert ensures your reloads meet exacting headspace and dimensional tolerances.

Sinclair International's gage inserts are manufactured to tight tolerances and function as mechanical go/no-go reference standards for large-magnum and belted rifle cartridges. The #20a designation specifically addresses larger-diameter shoulder designs found in magnum and specialized hunting rounds. This insert integrates into Sinclair's modular gage system, allowing you to swap caliber-specific inserts without replacing the entire assembly. The precision-ground surfaces ensure consistent shoulder contact points, eliminating measurement variables introduced by worn or improvised alternatives and providing the repeatability demanded in duty ammunition production.

This insert is ideal for reloaders working with magnum cartridges—.300 Win Mag, .338 Lapua, .375 H&H, and similar calibers—where shoulder geometry directly impacts feeding reliability and case longevity. Law enforcement and military ammunition sections benefit from using standardized gage inserts to validate production quality and maintain ballistic consistency across duty loads. Installation is straightforward within compatible Sinclair gage bodies; simply position the insert and verify it seats fully. For operators managing high-volume reloading operations or maintaining strict quality assurance protocols, this precision gage insert is a non-negotiable component of a professional reloading bench.