[Ad Astra]

In this case, a Russian-capture K98 Mauser. Typical (nicer than usual) Russian mixmaster with electropencil match on bolt.

Swallows the NO-GO headspace gauge, won't close on the Field.

Some say it's perfectly safe to shoot with factory ammo. Some say do not fire.

What do you think?

[ocabj]

Yes. I've got a Czech VZ24 with the same headspace condition. Closes on a no-go, but not on a field.

Whoever tells you that any rifle that closes on a no-go, but not on a field still isn't safe to shoot is uninformed about the concept of headspace gauges.

Go and no-go are only used during the actual barrelling process. Field gauges are used to determine if a barrel needs to be replaced.

[Ad Astra]

Appreciate the info. Heard the brass will stretch somewhat more if it fails NO-GO; OK since I'm shooting .5/round Yugo 8mm.

Would steel-cased Romanian 8mm have greater risk of cracking/case splits? Wondering.

and of course both gauges are the same brand: Forsters. Glad I bought the Field: always thought all you needed was a NO-GO and a cartridge.

[rockstar.esq]

So could someone please explain the finer points of this to me? If the idea is to have a chamber cut so that it'll close on a GO but won't close on a NO GO wouldn't a field be somewhere in between the two? After all aren't we talking about a depth of reaming situation? Unless I'm mistaken, the GO is shorter than the NO GO. I've never done any chamber reaming or rebarreling however I'd like to understand the process better.

[Erinyes]

So could someone please explain the finer points of this to me? If the idea is to have a chamber cut so that it'll close on a GO but won't close on a NO GO wouldn't a field be somewhere in between the two? After all aren't we talking about a depth of reaming situation? Unless I'm mistaken, the GO is shorter than the NO GO. I've never done any chamber reaming or rebarreling however I'd like to understand the process better.In order of length from shortest to longest it's GO, NO GO, Field. GO is absolute smallest size for a chamber to be in spec. NO GO is the largest for to still be in spec. Field is the largest for it still to be acceptable for use.

[foghornl]

My 1/50th of $1...

As I understand "headspace & guages"

"GO" is the smallest amount of headspace that meets original design specs.

"NO GO" is the maximum headspace...gun SHOULD be safe with 'New' ammo....i.e. not reloaded cases.

"Field" is field reject. TOO MUCH headspace to be considered safe. DO NOT SHOOT ANY GUN THAT CLOSES ON A "FIELD" GUAGE

If bolt closes on No Go, but doesn't close on "Field", it it generaly considered to be safe with "New" ammo, but Your Mileage Will Vary. I would try the "tie a string to trigger and stand Waaaay back" for the first firings on any gun that failed a No-Go. Examine the fired case(s) VERY THOROUGHLY for splits/cracks/rings/swells/stretch marks.

[ocabj]

Appreciate the info. Heard the brass will stretch somewhat more if it fails NO-GO; OK since I'm shooting .5/round Yugo 8mm.

Would steel-cased Romanian 8mm have greater risk of cracking/case splits? Wondering.

and of course both gauges are the same brand: Forsters. Glad I bought the Field: always thought all you needed was a NO-GO and a cartridge.

Yes, you are going to have case stretching. That's why if you plan on reloading the brass for this gun, you should neck size, or set your FL die for just enough shoulder setback.

You only need a field gauge for milsurp inspections. If you do your own rebarreling, you'll want the go and no-go.

[taliv]

in addition to milsurps etc, i'd say field gauges are useful for anything you pick up at a gunshow. e.g. a new BCG for your AR15

[Ian Sean]

The following is from a document on headspacing on Brownells website.

Modern headspace gauges are made of heat treated tool steel. Even though the steel is quite hard and tough, you must treat the gauges as though they were made of glass. If they are misused, they can break, cause damage to the gun being checked, or can give false readings on the correctness or incorrectness of a particular gun’s headspace and its suitability for use.

Our recommendation is that you use headspace gauges in sets from the same manufacturer. An example of this would be GO and NO-GO gauges from Clymer, and not one from Clymer and the other from Forster. Your results will be more uniform if you stick to this recommendation rather than mixing different brands. Under normal commercial circumstances, a gun whose bolt closes completely on a NO-GO headspace gauge (even if it does not close on a FIELD gauge) should not be put out for sale or returned to a customer as being suitable for use, until the headspace situation is corrected. Keep in mind that a firearm may have perfect headspace, but may have other
chamber problems or action problems that could keep it from being used safely.

There are normally three types of gauges made; GO, NO-GO and FIELD. The GO gauge corresponds to the SAAMI (Sporting Arms & Ammunition Manufacturer’s Institute) minimum chamber length, while the FIELD gauge usually matches the maximum chamber depth, or slightly less. NO-GO gauges are an intermediate length between minimum and maximum, that, technically, is a voluntary dimension. A firearm that closes on a NO-GO gauge and does not close on a FIELD gauge may not give good accuracy and may have very short cartridge case life from the ammunition re-loader’s standpoint.

Case head separations are a possibility with a gun that closes on a NO-GO gauge. It may also fail to fire or suffer from misfires, depending on the firing pin dimensions. Here’s a very thorough list of instructions on how to use headspace gauges to check headspace. It’s broken down by type of firearm and type of actions so you can hone in on the kind of firearm that you work on most.

[Ian Sean]

Complete document on headspace located here for those interested. http://72.14.209.104/search?q=cache:YYHUyC04Dx0J:216.243.198.184/aspx/NS/GunTech/NewsletterArchive.aspx%3Fp%3D0%26t%3D2%26i%3D41+headspace+gauges&hl=en&gl=us&ct=clnk&cd=7

My personal experience with Clymer and Forster gauges is that on some sizes the the NO-GO between brands are different by a few thousandths. The Go's and Fields are the same. Apparently the different brands differ on what size NO-GO is defined. I have found this on .30-06 and .308 in my experience with them.

[nbkky71]

Go ahead and shoot. Just be mindful and check the headspace from time to time. You can also try swapping bolts until you find one that falls between a GO and NO GO.

I had a re-barreled 1903 Mk1 Springfield that just closed on a NO GO gauge, but did not close on a FIELD gauge. I swapped bolts until I found the right one.

[Ad Astra]

The rifle won't get heavy use. I have other shooter-grade Mausers, and may try bolt-swapping with other RC K98's.

Interesting stuff and thanks. If all I had bought was a "Field" gauge, I'd have never known about it.

[Gromulin]

Anyone know where to find a Clymer FIELD gage in 30-06? I've got the GO and NO GO, but can't find a FIELD anywhere.

TIA

[ocabj]

I bought mine straight from Clymer via phone order. I ordered it with the extractor cut, but I still strip bolts on the Garand when I check headspace.