Sinclair #30A Shoulder Bump Gage Insert, 30 Degree, 300 SAUM/7mm/338

Description

If you've ever wondered whether you're oversizing your brass, this little piece of steel takes the guesswork out of it. The Sinclair #30A Bump Gage Insert drops into a comparator body and reads straight off the shoulder of your case, so you can set up your full-length sizing die to bump the shoulder back exactly where you want it. Rather than measuring to the datum line, it indicates off the shoulder itself, which gives you a cleaner, more usable read on how much you're moving the brass each pass.

The #30A is cut for a 30-degree shoulder angle and covers a wide spread of calibers, including 300 Remington SAUM, 338 Ruger Compact Magnum, 300 Ruger Compact Magnum, 25 WSSM, 30 BR, 30 Thompson Center, 300 Savage, 6.5 Creedmoor, 6.5 Grendel, and 6.5 BR. The inserts are engraved with the shoulder angle, so matching it to the right case is simple once you check your cartridge drawing.

Why the #30A Bump Gage Insert Earns Its Spot

Machined from stainless steel, this insert holds up to years of bench use without the soft-metal wear you get from aluminum. The taper is cut to mirror the shoulder of your chamber, so when you zero your caliper off a known reference and measure a fired case, you get repeatable numbers you can trust. For most bolt guns a .001 to .002 inch bump keeps brass alive and chambering smooth, while AR-pattern rifles usually like a little more.

Fitting the #30A Into Your Reloading Setup

This is an insert only, so you'll need a comparator or bump gage body to run it. It seats into either Sinclair comparator body and also works with Hornady and Stoney Point bodies, though the shorter Sinclair insert means you'll want the extended-length body if you plan to check shoulder measurements on loaded rounds. Secure it with a 5/64 hex wrench, clamp the body to your calipers, and you're ready to measure. A handy tip from folks who run these: mark your body and insert combo so you keep the same pairing for consistent readings.