Headspace can loosely be defined as the distance between the closed and locked breech face of a firearm and the point where the cartridge case touches the chamber. On a Bottle neck cartridge case this would be a certain point on the shoulder of the cartridge case. Belted cartridges would normally headspace on the front of the belt. Rimmed cartridges would normally headspace on the front of the rim, and straight walled rimless cartridges as in 45 ACP or 9MM Luger headspace on the rim of the cartridge. Correct headspace has an absolute perfect specification, but there is a small range of variation which is acceptable.

Excessive Headspace

The mystery then, is how much space is needed to allow the rifle to function easily and how much is too much causing an unsafe condition. Too much headspace will allow the case to stretch excessively. Headspace that is really out of specification will cause case head separation, possible gas leakage, and excessive wear and tear on the firearm as well as short life of your brass. Excessive headspace can be dangerous. Excessive headspace can be caused by wear, mismatched parts [especially found in old military rifles], and by improperly re-sizing of cartridge cases. Propper adjustment of your re-sizing die then, is a critical component of the reloading process.

Insufficient Headspace

Insufficient headspace can cause the firearm to be difficult to close with a cartridge in the chamber and may cause the firearm to be difficult to or impossible to lock without using excessive force. Insufficient headspace can be caused by improper assembly of a firearm, allowing cartridge cases to become too long, and improper resizing. If a cartridge is too long, the front of the cartridge may be squeezed into the throat of the firearm and not allow for enough clearance for the cartridge. Not sizing the cartridge enough to allow the cartridge to fit the chamber at the proper point on the shoulder will make for too tight a fit.

Checking Headspace

Checking headspace is easy enough to do if you have the proper gauges. Gauges are caliber specific and consist of a go gauge and a no-go gauge. The gauges conform to SAMMI specifications. Checking headspace only takes a few minutes but can save a lot of grief. Anytime there is any reason to suspect a head space issue, or any old gun that you may acquire should have the headspace checked before being fired. Bodily injury or even just damage to the firearm could be prevented.

Craig’s Outdoor Sports has a good collection of headspace gauges and access to others. If you need the headspace checked on a firearm, give Craig a call. Incorrect headspace can be a serious issue. Sometimes it can be corrected economically. Other times it may be that the firearm should be retired. Always it is best to know what you have.