Sinclair Shoulder Bump Gage Insert #26, 26 Degree, 6mm

Description

This Sinclair bump gage insert is the #26, machined with a 26 degree taper to match the shoulder angle of 6mm Remington cases. Instead of relying on a datum line, it rides directly off the shoulder of the case, which gives you a cleaner, more repeatable reading of exactly how much you're sizing your brass. If you're chasing consistent headspace and longer case life, this is the little piece that makes it happen.

How the Sinclair #26 Bump Gage Insert Works

The insert drops into a comparator body and clamps onto one of your caliper blades. You measure a fired case from head to shoulder, zero your calipers, then measure again after running it through your sizing die. The difference is your shoulder bump. Because the insert is machined to the actual shoulder angle, it also squares the case head up to the caliper blade, which is a big part of why the readings stay repeatable from case to case. Most reloaders aim for about .001 to .002 inches of bump on bolt guns and .003 to .005 inches for AR-style rifles.

Fitting the 6mm Shoulder Bump Insert to Your Setup

This is just the insert, so you'll need a comparator body to run it. It installs in either Sinclair comparator body and also works with a Hornady comparator body if you already have one on the bench. Securing it takes a 5/64 hex wrench. If you want to gauge loaded rounds rather than just brass, the longer comparator body gives you the clearance to do it.

Why 6mm Remington Reloaders Reach for This Insert

Precise shoulder bump keeps your cases chambering smoothly without oversizing, and that pays off in brass that lasts longer and ammo that shoots more consistently. Sinclair's stainless construction holds up to years of bench use, and the shoulder-matched design is a step up from generic headspace inserts that only contact at a fixed datum. For anyone loading 6mm Remington who cares about getting sizing dialed in right, it's a small tool that earns its keep.