July 18th 2023Five Cool Tool to Measure Shoulder Bumps on Your CasesThe Tactical Rifle Shooters Facebook Group has recently shown off tools used to measure headspace in cases before and after “bumping”. Hand-loaders who size their cases to full length will bump the shoulders anywhere between.001? Depending on the rifle, and the application, hand-loaders who full-length size their cases will typically bump back the shoulders anywhere from.001? We prefer.0015 for our 6mmBR and Dasher case. You want to have the same amount of bump and case sizing for all brass. It is important to measure your brass cases before and after FL sizing. This will ensure uniformity. We check each case when we have the time. Some folks will only check the first 3-4 case coming out of the FL die to ensure that the FL die setting and desired headspace/bump are correct. Whidden Shoulder Bump GaugeThere is a variety of tools available to measure shoulder bump. Whidden Gunworks makes a special bushing that is designed for cartridges. This is our favorite. The Whidden ShoulderBump Gauge allows you to adjust your sizing tool to the desired measurement. The bump gauge is attached with a set-screw to your calipers and measures the distance from the base of the case to the shoulder. The photo below is from Tactical Rifle Shooters and shows the Whidden Bump Gauge used for the.375 CheyTac Cartridge.2. Dave Manson Vertical Comparison with Dial ReadoutBackground image courtesy of Tactical Rifle Shooters. Inset photo by Manson Precision Reamers. Dave Manson says: “This tool is designed to make the life easier for advanced shooters and reloaders by allowing precise measurements of ammunition, chamber, and case headspace.” This information will allow the reloader to fine-tune the clearances and fits of his ammunition and chamber. This will result in improvements in accuracy and case longevity. The Manson Comparator has the following functions: Measure the headspace of factory or reloaded ammunition
2. Measure the headspace in a fired cartridge to determine the chamber headspace
3. When setting up reloading dies, ensure that the shoulder set-back is minimal.
4. Compare base-to-ogive length to ensure consistent bullet-to-rifling relationship.In addition to the Dial Indicator and Stand, the $150.00 Vertical Comparator is supplied with multiple Datum Blocks of precise length and inside diameter (.3300?/.3750?/.4000?/.4375?). MORE INFO HERE — Catalog page 29.3. Hornady Lock-N Load Headspace Comparator SystemHornady’s Lock-N Load Headspace Comparator is simple to use and convenient. Midsouth offers a kit that includes a Red bushing-holder and 5 bushings. The kit costs $43.43. Hornady explains that the Lock-N-Load (R) Headspace Comparer… gauge measures variations before and after firing. It allows headspace comparisons between resized brass and fire-formed brass. Hornady says: “To find the correct bushing diameter, add the neck diameter to the shoulder diameter. Then divide the result by two.” Use the bushing that is closest to this number. Hornady has five sizes:.330,.350,.375,.400, and.420. One tip — we have found that Hornady gauges can vary slightly from unit to unit, even though they are the same nominal size. Test each gauge on your brass if you have several for the same cartridge. You may notice a slight difference. Mark one and use it consistently. There is an Anvil Base Kit which mounts on the opposite blade of the caliper. This provides a more solid surface for your case’s base. L.E. Wilson Case Gage MicrometerIf you want to measure “bump” accurately without having to use calipers or clamp-on gauges, you might consider the L.E. Wilson Case Gage Depth Micrometer ($130.00 at present). This allows for repeatable, precise measurements. However, you must know your starting point. The manufacturer explains that “every reloader must know how much their Full Length Sizing Die pushes back the shoulder. You can now do this with the NEW Case Gage Depth Micrometer! It’s never been easier to take measurements of your case headspace before and following sizing. The Depth Mic lets you slip the micrometer over the top of Gage while your case is inserted in the Gage to take a measure. The Micrometer has graduations in.001?. The Case Gage Depth Micrometer has a zero of 0.100? Our factory uses a scale. We include a Gage Block to allow you to test Zero, and adjust if needed. Pistol Brass Case DIY Shoulder Bump GaugeLast, if you don’t have any of the comparator instruments shown above, is a “field-efficient” set-up. You can measure shoulder bump using a.45 ACP (or another suitable pistol case). Make sure that the.45 ACP is squarely trimmed and round. We recommend that you run it first through an expander and then size, trim, and chamfer it. Then, slip the.45 ACP over the neck of an unsized, fired rifle case. Remove the primer. Align the two rifle cases between your calipers, and note the length of the rims (See left photo). Then, using a full-length rifle case without primer, do the same, placing the.45 ACP over the neck of FL-sized case. (Right photo). The difference between these two numbers is how much “bump” you are applying to your shoulder. The difference in this case is.0015?. The amount of bump that you need depends on your chamber and load, but.0015 -.002? This is a good starting setting.
Similar PostsTags: Case Gauge, Shoulder Bump Tool Review, Whidden Gunworks
