Headspace gauges are an essential tool when building any AR. Checking for proper headspace helps to insure that a rifle is safe to fire, and should be done on each and every build as well as on any used firearm. We tend to trust that factory new guns are safe, and we check them before firing anyway. In the Everything AR shop we use Clymer gauges nearly exclusively.
Clymer is one of several companies that make headspace gauges, and they do a very good job. Each gauge is precision ground and hardened steel made to SAAMI’s ANSI tolerances. The gauges are available for most common calibers, and many of the gauges will function for a number of dimensionally similar calibers as well. A cross compatibility list can be found on Clymer’s website.
Dimensional consistency from gauge to gauge is exceptional. Each and every gauge that we checked measured exactly as it was marked. Other manufacturers that we tested were all within specifications, but none were as precise as these. As always, we will continue to search out and review the best tools to be had, but we really have no expectation of finding anything better than Clymer headspace gauges.
Each gauge is available as GO, NO-GO, and in the case of rimless rifle calibers, FIELD. Prices range from $29.00 to $45.00 for individual gauges, with sets being available for slightly less than than it would cost to buy each one separately.
Our only complaint about these gauges is that we prefer the way that Forster marks their gauges with the primary cartridge as well as others that use the same gauge. This can save you the time of looking up the compatibility chart if you are not familiar with the tool, and helps prevent buying unnecessary duplicates.