FORSTER - FORSTER 7.62 MATCH GAUGES

This Forster GO Headspace Gauge is a nicely constructed product that performs an often ignored, but very important function. If your bolt carrier group locks into battery against this gauge (the smallest of the three sizes), you are good to go. This is an absolute necessity if you are building an AR.

This Forster Field Headspace Gauge is a nicely constructed product that performs an often ignored, but very important function. If your bolt carrier group locks into battery against this gauge (the biggest of the three sizes), you have an unsafe chamber headspace and should not shoot your rifle until is it fixed. The only downside is the price, because its a very limited function tool. Bottom line, you need this tool(along with Go and NO-GO gauges) if you are building an AR.

This Forster NO-GO Headspace Gauge is a nicely constructed product that performs an often ignored, but very important function. If your bolt carrier group locks into battery against this gauge (the middle of the three sizes), you may have an unsafe chamber headspace and should try the larger FIELD gauge before shooting your rifle. If you are planning to build an AR, this tool is a must.

The SAAMI limit is actually 1.4736 so this 1.4696 gauge may prove to be more useful as a NO-GO gauge than a FIELD gauge in many instances (manufacturers often chamber to 0.002" plus over SAAMI mins and this gauge is SAAMI min plus 0.006). The alternative Brownells (Foster) FIELD gauge checks the true SAAMI max limit ("FIELD") of 1.4736 and permits 0.004 more headspace than this gauge. For further reference, the Foster NO-GO gauge is 1.4696 and only 0.003" above SAAMI min headspace and the Foster GO gauge is at the SAAMI min limit. In my experience, most AR bolts will close on the Foster NO-GO gauge and this "FIELD" gauge may actually be a better test for "NO-GO," unless all your barrels are custom-chambered! The best solution for checking headspace, post-chambering, is the full set of 11 Foster gauges offered by Brownells. It provides 0.001" resolution over the entire 1.4636" to 1.4736" SAAMI range, which includes any 5.56 specs and limits too. (5.56 headspace specs all lie withing the SAAMI min to max range.)

In studying the prints for many 5.56 and 223 chamber reamers and the SAAMI 223 Rem spec, I discovered that headspace gauges and chamber reamers are all over the map. This Forster NO-GO gauge appears check a rather arbitrary point within the SAAMI min to max headspace spec range so one can't draw much of a conclusion based on a gun failing a check with this NO-GO gauge. More specifically, the min to max SAAMI headspace spec spans 0.010 inches. The Forster GO gauge checks the bottom limit of the SAAMI spec and the Brownells (Forster) FIELD gauge checks the upper limit. Various NO-GO gauges fall in various places with respect to 5.56 and 223 Rem specs, but these intermediate gauges (including 5.56 gauges) all lie between the SAAMI 223 Rem min and max headspace limits. The problem is this Forster NO-GO gauge checks only 0.003" above the min SAAMI spec. I've learned that barrel manufacturers often chamber their barrels 0.002" longer the SAAMI minimum (the manufacturers use SAAMI min + 0.002" as THEIR mininum manufacturing spec), due to the dangers posed by "tolerance stackup" of parts and insufficient headspace. Given that the Foster NO-G0 gauge is only another 0.001" longer than these barrel manufacturers' min chamberings, it is common for a bolt to close on this Foster NO-GO gauge. While the Foster NO-GO gauge provides a sensible limit for custom chambering new barrels, its usefulness is very limited for checking existing barrels where a safety check can be accomplished with only a GO and FIELD gauge set. Given where most barrels are headspaced, a NO-GO gauge close to the middle of the SAAMI range would be more useful. Even more useful is Brownells ".223/5.56 Match Headspace Gauge Set. It can be used to fully assess the headspace of an existing barrel.