Checking headspace on a revolver is easy and requires very little special equipment. If you are using a set of headspace gauges, each gauge is placed in a chamber, and the cylinder is closed to verify that it is within prescribed tolerances.

When you have a gunsmith shop, there are some jobs that folks will ask for on a pretty regular basis. You’ll mount scopes, install recoil pads, glass-bed actions, and replace broken parts. These jobs keep you busy and help pay the rent. One of the more frequently requested jobs is to check headspace on a rifle. It seems most gun owners are aware of the importance of headspace and want to make sure their rifles are headspaced properly.

Oddly enough, I seldom have had a customer ask me to check headspace on a revolver. Sure, I often do this as part of other jobs, such as safety checks or diagnosing other problems in a wheelgun, but I probably have had no more than a dozen or so customers ask to check the headspace on their revolvers.

Headspace on a revolver can be just as important as on a centerfire rifle even though you seldom encounter situations where the negative consequences are as grave. Seriously excessive headspace in a high-power rifle can lead to a ruptured cartridge case and the release of hot gases under tremendous pressure into the action. If the gas escapes back into the shooter’s face, the results can be disastrous.

Let’s take a look at revolver headspace and how to check it. It’s a bit different than with most rifles, but if you’re a revolver shooter, you might want to know more about this. You never can tell when you’ll want to check out a revolver, and yes, you can check headspace without using headspace gauges, but there are some things you need to know to do it right.

Headspace in a standard double-action centerfire revolver that fires a rimmed cartridge, such as the .38 Special, is measured from the point on the cylinder that supports the cartridge rim to the vertical face of the frame, or breechface, directly behind the cylinder. The gap between these two points must be large enough to permit the cartridge case to fully seat in the cylinder chamber yet small enough to support the head of the case when the cartridge is fired. If there’s excessive headspace between the rear of the cartridge case and the face of the frame, the cartridge will not be supported. Upon firing, the cartridge case will move back out of the chamber until it is stopped by the frame. That’s well and good, but the side of the cartridge case immediately ahead of the rim is no longer supported within the chamber. Depending upon the pressure of the load, the unsupported case could bulge or even rupture. This could damage the gun and possibly injure the shooter.

If the gap between the cylinder and the breechface is too small, then it may be impossible for the cylinder to lock into the frame or rotate properly when the gun is loaded.

For many years, the firearms industry group known as the Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) set standards for critical dimensions for firearms and ammunition. According to SAAMI, the minimum acceptable distance, or headspace, between the rim seat on the cylinder and the breechface for a .38 Special revolver is .060 inch. The maximum acceptable headspace is .074 inch. Thus we have a tolerance of .014 inch between minimum and maximum headspace. As long as a revolver meets these standards, it is considered to have proper headspace. Gauges are produced to measure these critical dimensions. The gauge equivalent to minimum headspace is normally the “Go” gauge, while the gauge equal to the maximum headspace is often, but not always, the “No-Go” gauge. More on that later.