Gauge Use

This category covers the function and use of the gauges

Factory ammunition not fitting the gauge is not an indicator of a defective gauge. The gauge is the reference tool, the ammunition is what you are inspecting. More likely, factory ammunition not fitting the gauge means the factory ammunition is out of spec. This could be from something that occured to it during shipping/handling, or it could be slightly out of spec/tolerance from the manufacturing.  It is also possible to have dirt/debris on the ammunition or gauge that needs to be cleaned off. Does all of that particular ammunition fail the gauge, or just some of it?  Can you identify where it is sticking in the gauge? This does occur, and usually the ammunition being out of spec is the issue. But we are happy to help you diagnose this, so send us a message so we can help you and make sure that the gauge is working properly.

The gauges are made to the minimum chamber dimensions. Most chambers will be larger than this. So it will reject some rounds that may still fit your chamber.  If you only use the gauge as a pass/fail chamber checker, any rounds it passes should fit into your chamber without an issue.

But using the gauge just as a pass/fail chamber checker is missing its use as an inspection tool. The slot makes it easier to pinpoint interference, and the 3 steps on the face are directly pulled from the headspace reference specs for both the cartridge and the chamber.

Since the dies and other parts in the reloading process are all designed around making ammunition that will fit an in spec chamber, then the question should be why wouldn't it fit the gauge?  Even if it does still fit your chamber, the fact that it is failing the gauge is telling you there is something in the loading process that needs to be looked at. It could be a problem with neck thickness or concentricity on brass formed from other calibers. It could be neck bulges from the bullet seating process. It could be that the bullet is not seated straight. It could be burs on the case mouth from cutting the case. There are a long list of other potential problems that can be found using the gauge as an inspection tool.

Some people just want it to fit the one firing chamber they test it in and aren't concerned about any quality control beyond that.

Our slotted gauge is patented, with the following utility patents: US9513097B1 and US9863748B2 . Manufacturers who are interested in licensing are welcome to contact us.
Other companies case gauges are only the length of the case, and often have a step on the end to indicate trim length. Our ammunition gauge and slotted ammunition gauge are the full cartridge length (COL), so they can not have a step on the end of the gauge to show trim length. On most pistol cartridges where the case headspaces directly on the mouth, the need to trim will be indicated by the headspace measurement. Our gauge will show this clearly. On rifle cartridges, where the cartridge headspaces on the shoulder or a belt(for belted magnums), there should be some space between the mouth of the case and the corresponding end of the chamber. So you can not use the gauge to check for the trim length. This can be checked with calipers.      

All of the standard and slotted gauges are made of 303 stainless steel, and should resist rusting and oxidation. They can be cleaned with normal CLP type cleaners. For best results in gauging, they should be cleaned regularly to reduce the chances of any residue from the brass or ammo building up inside the gauge.

There is a good bit more work that goes into slotting the gauge than just a few minutes cutting the slot. As mentioned previously, the gauge has very tight tolerances. So after the slotting the slots have to be very carefully cleaned and deburred. Any small error in this could mess up headspace measurements or the diameters. So while it is certainly possible to have a machine shop mill a slot in it, you may not get the results you want. And I would not recommend this.

As far as slotting other brand gauges, it is a question of utility. If the gauge is oversized in diameter so that it only is useful for checking headspace or trim length, what will you gain by seeing the slot? You can't check the profile of the cartridge against the gauge because the profile of the gauge is oversized.

Also, please keep in mind that our slotted gauge is patented, with the following utility patents: US9513097B1 and US9863748B2. 

Comparators do not measure case diameters, they only take the headspace measurement. They are useful for setting up your dies, but are not useful for doing a complete chamber check. Like some case gauges mentioned above, they will accept an oversized round, so you could check the headspace length to get an accurate measurement of a fired case.

Comparators will provide a measurement, while the gauge itself gives you a simple and quick pass/fail reading. With our gauge, and case gauges as well, calipers could be used to measure the protrusion of the cartridge above the face of the gauge, or above the steps in the face of the gauge. So you can use them to get a measurement with the assistance of calipers.

Just using calipers can get you very accurate measurements to compare against the cartridge specs. There are only two real downsides to this. The first is time. If you are going to check your loaded rounds with calipers, you are going to be spending a lot of time doing it. The second downside is that you are only looking at the single measurement, not how it is tied in with all of the other measurements. All of the measurements on the gauge are tied to the same centerline. A bullet seated at an angle could measure just fine with the calipers, but fail our gauge and not chamber. A concentricity or runout measuring device would give you a good indication and measurement of problems like that. Our Ammunition Gauge will indicate this issue, and much quicker too.

With that said, if you do not own calipers, I would suggest getting them before any other measuring tools. They are useful for many applications, not just reloading.

In addition to all of the differences between the other gauges and our standard gauge, outlined above, our slotted gauge has some very unique advantages. The slot effectively allows you to see how the cartridge fits into a tight chamber. This allows you to visually check that the shoulder is seated properly when you are checking the headspace measurements. If there is any other interference, you can see that as well. It allows you to inspect the entire profile of the cartridge, instead of just seeing if it sits flush in the gauge or not. And it makes it much easier to remove tight rounds.

Our gauges are designed to check against a tight SAAMI chamber so that what fits in the gauge, should work in any firing chamber. If you are not concerned about making ammunition that is within spec, or is capable of working in any gun aside from the one you are loading it for, you may want to use a different tool, or no tool at all.

There are several functional differences between our gauge and others. It is a good idea to know these so you can decide which gauge best suits your needs. Our Ammunition Gauge is designed to include the chamber throat, so you can see whether the complete loaded round is within spec. Most other case gauges are designed to just measure the case. As a result most other gauges do not include the throat, but may include a simple check to see if your cases need to be trimmed.

Some case gauges are designed primarily to measure the case headspace and case trim length. In order to do this, they are cut with a larger diameter than normal. This is intentional, and allows cases to drop in, regardless of diameter. The downside of this is that they are not useful as a chamber checker. Problems that could cause a jam such as thick necks, oversized bases, case bulges, and bullet seating issues may not be caught by a case gauge, but can be identified with our gauge. The gauge manufacturer should state whether their case gauge is cut to a larger diameter or not.

Our gauges are designed to check against a tight SAAMI chamber so that what fits in the gauge, should work in any firing chamber. If you are not concerned about making ammunition that is within spec or is capable of working in any gun aside from the one you are loading it for, you may want to use a different tool or no tool at all.

The face of the gauge is equal to the max acceptable headspace length of a SAAMI spec chamber. The middle step is the minimum headspace length of a SAAMI spec chamber. An in spec firing chamber will be somewhere in the range of these 2 slots. To make brass fit any SAAMI spec firing chamber, it should be at the level of, or shorter than the middle step.

The lowest step is the minimum SAAMI spec brass length. If brass is made between the middle step, and and lowest step, it should be in spec, and also fit any in spec firing chamber.