Home Forums Hunting & Shooting Gunsmithing used guns and go, no-go, and field gauges

A few questions:

It seems to me that only a no-go gauge is really needed to check headspacing of a used gun from a safety perspective because headspace problems on the short end would result in a round not chambering, and a no-go gauge would be definitive from the perspective of too much headspace. Is that the case, or would a field gauge be better to use for checking the headspace for used guns? I guess the bottom line is how should I be checking headspace for used guns (and probably for that matter factory new guns)?

How often do you see guns with too little headspace?

What is the use of a field gauge? It seems like a no-go gauge would be the one for checking for excess headspace and a go gauge would help in installing a barrel to make sure the barrel wasn't installed with too little headspace, but the field gauge seems to be caught in the middle without a good reason. However, its existence causes me to think it must have a purpose - what is it.

Is Forster the only game in town for headspace gauges? The Midway price seems reasonable at $18.49, but if there are equally good gauges for half that, I can't see paying a premium unnecessarily.

Thanks.

you will use these headspace gages for a lifetime or more. forster is OK but clymer is better. if you do rebarreling it is best to get all three gages. sometimes if the bolt closes on the no go it may still be safe and thats where the field gage comes in. i guess that just the no go for used gun inspection prior to purchase would work. once in a while an home grown barreling job will not close on the go gage but the pipe wrench marks on the barrel and receiver could be visible! : )

I use Foster no go gages to check the guns that I buy. If the rifle takes the no go and you really want it then cut a tab of metal from a beverage can, mic it at about .003", and drop it on the end of the gage when its in the chamber.

I can work with a rifle like that with about .003" over the no go.

SAAMI specifies the headspace on all their chamber drawings, and lists the tolerance in each case. Typically a rimless cartridge chamber tolerance is plus .010", and a rimmed cartridge chamber is plus .007". A GO gauge is supposed to be at the minimum chamber dimension, and NO GO gauges are typically about plus .004". These gauges are the proper gauges to use when rebarreling or rechambering. For a rifle which has been used, the FIELD gauge tells you if the wear on the gun has rendered it unsafe for further use. This gauge is out near the outer limits of the SAAMI specification.

Savage99,

Have you found many used 99's that wouldn't close on a field gage?

I've checked my small accumulation of these rifles that are chambered in 300 Sav or .243/.308 since those are field gages I have, and have found all will close on a FG. Only one of my 99's went to the 'smith to address this, a 30-30, that was backing primers out too far to suit me.

IMHO, I'd pass on that rifle.. Or, use the info to negotiate a lower price if possible, then fix the headspace issue.. You're most likely relatively safe IF the round is a low-pressure round, but anything else should be corrected.

Rarely, but I have one in the shop now for a rebarrel that not only was short, but the chamber was ruined from a previous 'smith' (using the term loosely in this case). The owner couldn't get a factory shell to chamber.. Sent the rifle to me. Checked with a GO headspace gauge and the bolt wouldn't close.. Removed the barrel and inspected the chamber; hoping just a touch-up with the reamer would give me the .001-.002 needed. A light revealed much chamber damage, rings, gouges, etc... It's toast.. The caliber/casing is such that a setback to correct was impossible without removing probably at least a half-inch of shank..

I do not have any field gages. Of the two 99's that I have, both .358s, one has excessive headspace however I don't know how much. I make brass for it from new 30-06's. This one is my original from 1966 and has been fired thousands of times some of which may have been hot loads.

The other seems ok but I have not measured it.

Edit: I now recall a cute 38-55 that I had with excessive headspace. There was no easy fix for me so I sold the rifle.

Savage 99

Thanks for the response.