#35 35\ Shoulder (up To 338 Caliber) Bump Gage Insert

The Sinclair International #35 35" Shoulder Bump Gage Insert (up to .338 caliber) is a precision reloading tool designed for handloaders who demand accuracy and consistency in custom ammunition development. This insert serves as a critical measurement device in the cartridge development process, allowing shooters and reloaders to fine-tune rifle chamber pressures and bullet seating depths with laboratory-grade precision. Whether you're optimizing loads for competition shooting, long-range hunting, or precision rifle work, this gage insert eliminates guesswork from the shoulder-bump measurement equation.

The #35 insert is engineered to measure the shoulder datum line of bottleneck cartridges up to .338 caliber, making it compatible with common magnum calibers like .300 Win Mag, .338 Lapua Magnum, and similar large-bore rifle rounds. Bump gages work by establishing a reference measurement from the cartridge shoulder to the case head, allowing reloaders to determine precise neck-to-shoulder clearance and brass life. The insert's compact design and lightweight construction (0.05 lbs) make it an essential component of Sinclair's modular gage system, integrating seamlessly with standard reloading benches and measurement protocols without adding bulk or complexity to your workflow.

This gage insert is ideal for serious handloaders, precision rifle competitors, and gunsmithing professionals who work with magnum rifle cartridges and require repeatable, auditable load development records. The insert works in conjunction with a Sinclair gage body and digital or dial calipers to produce consistent, measurable results across multiple fired cases and reloaded rounds. Proper shoulder-bump measurement directly impacts case longevity, pressure consistency, and overall accuracy—making this tool indispensable for anyone seeking to extend brass life and achieve tight velocity spreads in match-grade ammunition.