Q. : I just purchased a Forster “go” gauge for my 223. The dimension stamped on it shows significant digits to +/- .0001”. What concerns me is that when I measure the gauge using my Hornady cartridge headspace gauges, the measurement is more than .005” different than the value on the gauge. Why is that?
A. The chamber headspace gage you purchased from us (our part# HG0223G) is made to the dimension etched on the tool. There actually is a + .0003” tolerance on our manufacturing process for GO gages. Hence, the gage may be anywhere between 1.4636” to 1.4639”. That is not a very big spread at all, but we use very exacting tooling and measurement instruments that are traceable back to NIST certified measuring blocks.
The cartridge headspace gage you attempted to “measure” our chamber gage with, is really designed to make accurate relative measurements for comparison only. It is not a precision tool that is capable of calibrating headspace gages exact lengths. For example, the cartridge headspace tool is very good for measuring a large sized sample of fired cases from rifle. The results of these measurements can then be recorded and an average length calculated. Then, after full length sizing the cases with your sizing die, you can re-measure the same sample of cases to see how much shorter they are after full length sizing. The relative difference in your measurements of fired vs. sized cases should be very accurate. This information can be very useful in setting up your sizing die to better fit ammunition to your rifle’s chamber.
Posted in: Headspace Gages FAQs