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.