Does anyone know the difference (in thousandths)in chamber depth between a "go" and "no go" guage and between a "no go" and "field" guage. I understand that a "go" guage should represent the SAAMI minimum chamber, or in other words to insure that all factory cartridges will chamber your bolt must close on a "go" guage

As I recall (off the top of my head, may be way off) the field gauge is 0.004" longer then the go gauge, and the no-go is 0.006" longer then the go.

It depends on caliber. Rimless bottleneck is usually Go= zero and No-Go = +.007 Belted mags are Zero and plus .004. Some English express calibers are plus .010.

I've been a professional gunsmith/maker for 33 years and have yet to own a No-Go gauge. I use a Go and an indicator to measure the slop with. I want to KNOW what the excess headspace is, not guess at it.

I Know this from from a P-17,go 0,no-go +.006,and field +.009.

Mr. Belk,

What do you like to set your headspace at? is there a magic number you strive for?

-Mike

z1r--
I shoot for zero slop on a GO gauge....and the barrel isn't marked with name and date until it is. That's the ONLY way to keep track of action wear.

It's surprisingly easy to set everything to zero if the action is square and straigt and the lug recesses are good.

jeffeosso--

What "lathe error" would make me misread the depth mike? I chamber barrel blanks and reset headspace on worn actions and improved chambers with the barrel off the gun. All measurments are taken directly on the gauge and on the action.

A rifle with set back lugs wont usually close on a No-Go and still have unsafe excess headspace. (send me email if you want the text file that describes it.)

No-Go gauges were introduced in WW-I as a fast check in the field. Not for the builders that made the rifle. A rifle is built from a zero datum line. Tolorences can be different, but all measurements are taken from the datum.

Jack,
A side note, have you ever heard of the Headspace Gauge set made by the Oregon Gauge Co. of Carlton, Oregon. It supposedly measure the exact dimension in the chamber of a number of cartridges all based I would imagine on the parent cartridge. I have a chance to pick one up.

Chic---

I haven't heard of that one. Keep me posted. Most of my old Clymers are so faded I'm having trouble reading them.

jeffeosso--

It's all a matter of technique.... I rough out the chamber with drill bit then ream from the tail stock chuck until the pilot engages and a shoulder in formed. From there the reamer is supported by the tailstock center and the job slows way down.

When measurements are taken at close to the end they're always taken in sets of threes with a complete cleaning between them.

Compressed air and a hard wipe with a dry paper towel on a bore brush will clear chips from the chamber but I clean, measure, clean, measure, clean and measure again. Belted and rimmed cases don't pose as much problems. You can SEE those surfaces.

The fact is that so many measurements are taken over the period of fitting the barrel that mistakes are limited to the wrong gauge and bad math. (easy to do with a depth mic, which reads in reverse.)

Believe me, before the final test with a live round in the swimming pool the headspace is correct.

IF you have a GO gauge and know how to check headspace.. Clean chamber and *totally* stripped bolt...a NO GO gauge is wasted money. Insert the Go gauge and measure the amount of bolt movement and that *tells* you how much EXCESS headspace the gun has. I think knowing the actual figure is much better than just knowing "it has some, but not too much."

I once ended up with a 30/06 no-go guage that came in a boxof stuff I bought at an auction. I kept it around, unused until I picked it up by mistake and chambered a barrel .006 too deep. The guage twinkled nicely as it flew through the air. It is presently up on the hill behind the house which is it's proper place.
It is as Jack said, With a go gauge and a depth mike or indicator you can measure the headspace. The no go guage is a quick check item only and really of no real value in the shop. Regards, Bill.

Jack,
You're absolutely right, there's no substitute for accurate measurements with quality instruments. Go and NoGo guages are a crude, quick way of measurement in the world of machining and are only used for a quicker and less precise method of measurement. I've yet to see a chambers and headspace dimensions taken to SAAMI specs that shoot worth a damn. If you want something to shoot well, It's gotta be closer than their callouts.

jeffeosso,
I would suggest that if the "newbie" does not have or has not aquired enough expertise to properly chamber and check his work with precision instruments, he has no business building a rifle. He's a liability to himself and others. I think too many people getting into the business of building rifles,take the job too lightly. When you pull the trigger on your rifle, you're producing an explosion that can produce in some cases over 65,000 PSI. This explosion takes place a mere few inches from your face. All of your measurements and calculations become hyper-critical at that moment. This is the time when you better have your sh#@* together, or you'll be carried from the range, rather than walking.

Say you're just a chump like me, no lathe, no barrel vise, no fancy measurement tools and all factory built guns. If my gun closes on a no go guage it's off to the gunsmith. I'm not up for stripping my bolts (spring ejector types anyhow), so what good does a go gauge do me?

In all honesty I don't have either.

How about those RCBS gauges that measure the length of fired cases? Are they accurate enough to detect any problems? I can't imagine that all brass springs back the same.

Jeffeosso,
Don't get me wrong here, I'm not trying to give you shit about suggesting that the guy would be safer by using a NOGO guage to check his headspace with, it's better than nothing. Just keep in perspective that in order to properly set-up a rifle initially, It's to the point of useless. If you really needed it you've already screwed up.

As for insurance on some fool taking it on himself to do his own gunsmithing, there's only one real solution, SPC (Statistical Process Control). No rifle should leave a gunsmith's door without proper documentation of dimensions and processes performed on it. The same can be said about trigger adjustments. We epoxy the screws on Remington triggers and color the epoxy with our own special color. If you tamper with the screws we'll know about it. It's saved our bacon a couple of times over the years. One can never be too careful when comes to such things.

Sorry about the misunderstanding. I just get nervous when folks like to try some things on their own without getting a proper education first. That can be bad for everybody. The proper fitting of a barrel to a receiver can't be overemphasized.

Jeffeosso,

I really don't see where anyone was giving you SH*T. I think they were merely stating that they prefer to know exactly what the headspace is rather than knowing what range it falls in. There is a world of difference in headspacing a rifle and merely checking one with a headspace guage.

I think Matt also brought up a very important point. These days everyone seems to be selling gunsmithing equipment and tons of people seem to be building their own rifles. I attended a class recently given by a local "Gunsmith" that scared the heck outta me. I wouldn't consider myself a Gunsmith yet but hope to someday. Anyway, the things I saw this so called professional doing would leave you stunned. There is no way I would ever fire anything he worked on. His methods were just too crude and lacked any real attention to detail. Just because someone thinks they can rebarrel a rifle doesn't mean they should.

Verrrrry interesting. I do own a few no-go gauges. They were all given to me and I'll be damned if I can remember ever using one. WHen I chamber a barrel it is always to minimum SAAMI specs. After assembly, If the go gauge doesn't feel right or I don't feel right about it, a simple .0015" piece of shim stock tells me if the chamber is too deep. And what the hell is this drivel about Pac-Nor not selling any more short 0r long chambered barrels. Any idiot worth his salt should be able to tell if you have to cut or chamber the damn thing. Sheeeeshh, go away and get some sleep.

I'll try an analogy-----

I tire gauge that reads <LOW> <JUST RIGHT> and <TOO MUCH> is great for the glove box, but the tire shop should have a gauge that reads in pounds.

So tell me gents.
What is the purpose, purportedly of the field gage?

If the NOGO is shorter, and it means something is wrong, is not then the longer field gage redundant?

Not trying to stir the @#$@ just wondering about the history here.....

Customstox & Jack Belk. Here are those gauges on Ebay. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1866882365

Joe M---

The "Field" gauge is a military invention.

If it fails the field gauge the case is likely to seperate during battle. Those guns are pulled from service.

I always use the guages. I want the chamber to be snug fitting on the go guage and I just use the no-go to make sure I haven't had a mess-up some where. I agree with Matt that the chamber should be tighter than current SAAMI tolerances. And as Jack wisely said, you should always check more than once. Something that hasn't been mentioned that I've run into. I have at various times ended up with more than one set of the same guages but from different manufacturers. Every time that I can remember, they were not the same. I have a 280 Rem go-guage from one company that is the same as the no-go I have from another. Now somebody has to be wrong. I sent the "tighter" set back to be checked and was told they were right. But what happens to a guy that doesn't know any better? He's got a real sloppy chamber. So all guages are not created equal.

Philinms

Here are the specs on a few of my headspace guages, all Clymer.

.223 Rem Go 1.464 No Go 1.467
.22-250 Rem Go 1.574 No Go 1.579
.257 Roberts Go 1.794 No Go 1.800
30-30 Go .063 No Go .067
30-06 Go 1.940 No Go 1.946
8 X 57 G0 1.8743 No Go 1.8803
45-70 Go .071 No Go .079
Belted Magnum Go .220 No Go .223

As you can see there is a big variation between go and no go depending on the cartridge.

If you use a head space guage it is important that you strip the bolt so that the extractor, firing pin, striker or ejector plunger as the case may be can not interfere and give you a false reading. It is very important that you close the bolt very lightly preferably with only your thumb and fore finger and feel the resistance with a delicate touch as the chamber and possibly guage can be easily damaged.

I hesitate to get in the go, no go guage debate but here goes.

On Jacks situation he apparently pretty much specializes in fitting barrels to bolt action rifles and building custom bolt action rifles, and very fine ones too. So you can use a go guage to referance all your measurements from and when you are through you can close the bolt and just feel a slight touch on the go guage or perhaps with a .001 shim but the bolt will refuse to close on a .002 shim. I use the same approach when fitting most barrel jobs. The other day I fitted and chambered a customer's action to 7.82 Lazzeroni Warbird and when I ordered the reamer I only ordered the go guage and reamed the chamber so the bolt would close easily on the go guage but when I inserted a .002 shim it refused to close. So I know that there is .001 headspace.

However some of you guys have failed to consider that if you do general repair that both the go and no go guage is needed. You need to be able to check suspect firearms in a business like manner in front of the customer, you can demonstrate right in front of him what the problem is. Likewise I get a lot of older guns to be checked for being safe to shoot and one of the items on my check list is head space. If I'm ever in a law suit I want to be able to testify that I used the best methods and tools available to determine the firearm was indeed safe to fire. If Johnny Cochran found out there were no go guages readily available and you did not use them..............One more thing I do to cover my axx is I always test fire three rounds, factory when available, then I give the customer one and I keep two with the job number date and customer name engraved on the case.

Jack.......I've been looking for ideas to build a better bullet trap but I dont think I can afford to put in a swimming pool. Seriously do you know of anyone who has built a good one? Not the old sand in the bottom of a pipe type but maybe an inertia type.

Craftsman---

Tricon Metals of Birmingham, Alabama can bend a piece of one-inch TriBlaze steel into a snail-type trap. It's expensive. I built a staggered baffle trap using old front-end loader lips from 3" manganese steel. You can draw one on graph paper to get the angles right. Mine lasted for nearly ten years before it ate up the first primary baffle. I made the first strike 15 degrees, the second 30 and the final 45 degrees. It's VERY important to have a small, padded, barrel entry point that only allows the bullet to travel straight towards the proper deflector. I had two pieces of heavy conveyor belting about 8 inches apart with the barrel hole in them. Don't shoot unless the barrel is through both rubber baffles.
I was still nervous shooting the big uns "down the tube" but never had any splash back with it.

Checking headspace---
I use a small magnetic indicator base to attach a test indicator to the rear tang, rear bridge, or, more often, the jaw of the vice.

Strip the bolt, insert the GO gauge, close the bolt and hold it forward against the gauge. Zero the test indicator on the back of the bolt. Now pull the bolt back against the lugs and READ how much headspace there is.

I don't leave .001 slop. The bolt handle should close to within five degrees of closed by it's own weight. You can feel the last 5 degrees when you close with one finger. After a dozen rounds or so the "feel" will dissapear but the headspace remains zero.

It's very easy for me to recheck any of my rifles for wear or set back in the lugs.....I checked a Sako 25-06 barrel marked BELK -70 (1970) this spring. It had .0004 headspace after about 500 rounds. That'll do.

I'll post a description of the danger of using a NO-GO gauge. The interest in this thread means it should be posted again.......with a picture.

Look for the thread-- Checking headspace---one way.

JBelk

I have no doubt that you technique of checking headspace is a sound one. But suppose you build a rifle for some one, and they get careless with their reloading and the rifle blows up. They get injured and decide to sue you claming the gun had excessive headspace. Wouldn�t it be better if you could produce as evidence a set of go and no-go gauges made by company X as your means of checking headspace, than to try to explain, or demonstrate you technique of using measuring instruments. And if it were found that the go or no-go gauges were faulty, liability would revert from you back to the manufacture of the gauges.

Todd--

I'd much rather defend the Actual measurement.

I would be critized for depending on a flawed technique for *measuring* headspace when it's easy to show how it can give a false reading.

The use of a NO GO is a *fast* way to determine the headspace *might* be right. No way I'd defend that in court. It's too easy for the lawyer to show you how it's uncertain... (I've seen .012 excess in a new rifle because there was a burr on the locking lug recess.)

The first substantial question by the plaintiff's lawyer would be, "At what point is headspace dangerously excessive?"

There's only ONE measurement that *nobody* can say is dangerous.....*Zero* excess headspace. That's the measurement I can testify the gun was delived at and demonstrate how it's done.

Interesting post on the CMP site.

Subject: Insufficient chamber headspace in M1903 rifles.

CMP has received reports that a few M1903 rifles shipped to customers have insufficient chamber headspace. This was discovered when the customer encountered unusual resistance when attempting to close the bolt on a chambered cartridge, or the bolt could not be closed at all. Thus far the problem involves only rifles freshly rebarreled with WWII replacement barrels, which were manufactured with �short� chambers to allow finish reaming for correct headspace after installation. CMP has concluded that a small number of these rifles were not correctly finish reamed at the arsenal. Insufficient headspace (unlike excessive headspace) does not present any significant safety hazard in an M1903 Rifle. However, it can interfere with proper functioning and should be corrected. Until recently CMP checked rifles for excessive headspace only, using a �no-go� gauge. CMP is now rechecking all rifles in house with a �go� gauge to assure minimum headspace as well. If you experience unusual resistance in chambering a cartridge, first unload the rifle and make certain the chamber is clean.. A heavily fouled chamber will produce the same symptoms as insufficient headspace. Brush out the chamber with a bronze or bristle brush if necessary. Then try to chamber a standard U.S. military M2 ball service cartridge. If it is still difficult to rotate the bolt closed, discontinue using the rifle. Do not try to use the rifle by slamming the bolt shut or forcibly turning the bolt handle down. Contact CMP for instructions to return the rifle for repair.

Somewhere back there someone mentioned the no-go gauge as being shorter than the go gauge. Am I all wet or is this really true. Let's clear up this confusion; if the no go is shorter, then what in the hell d o we need a go gauge for. I think I am correct in assuming the go is shortest, no-go next and longer and the field gauge is the longest. Geeez, someone help me out here.

Hello Jim,

Didn't read all of the replies, but the NO-GO gage should definitely be longer than a GO gage. Should chamber a GO gage to ensure that chamber is at least minimum, and should NOT chamber a NO-GO gage, which checks to make sure the headspace is not above maximum.

Bill

[ 10-16-2002, 18:56: Message edited by: Bill M ]

I do understand this and that, what I was trying to get across is someone's ineptitude and I was being a bit facetious.

Jim

Jim,

You have confused the no-go and field gauges.

Think of it in this sequence. The go gauge establishes minimum headspace. If the go gauge won't chamber, then the chamber isn't deep enough to chamber ammunition within the ammunitions specifications.

A field gauge is used to establish when headspace has exceeded minimum specifications, but still may be "acceptable". A newly built rifle should not close on a field gauge, but a used rifle can, and be "acceptable".

A no go gauge is just that. If the action closes on a no-go gauge, then it is unsafe for service.

Field gauges were developed for military weapons, to determine when wear was being developed in the action, and at what point the weapon would need to be returned to the arsenal. For sporting weapons, the field gauge is seldom if ever used.

Good gunsmiths work to much tighter tollerances then manufacturers. That is why you've heard the gunsmiths decry the use of the gauges. The factories on the other hand can crank out 100's of rifles at a time before having to worry about their chambers falling out of spec.

On a related item. Me and my old buddy Mike Bellm sat down one day back in 1982 or there abouts, and discussed headspace and belted magnums. We took a bunch of factory new brass at the time for the 300 Win Mag cartridge and began measuring the actual distance between the forward edge of the belt and head. We were somewhat surprised to see that a spread of as much as .013 existed amongst the brass. We always knew there was an accuracy problem with belted brass calibers and that the major factor affecting the accuracy had something to do with the belt.

It was decided that we would headspace these critters so that the bolt would not close on a magnum go gauge and that seemed to work pretty well. Being custom gunbuilders, the bulk of the work came from serious shooters who prefered to use nothing but handloads so this made things a lot easier. Now the chamber was cut to allow the customer to fireform his brass and then headspace in the conventional manner, ignoring the belt completely, although, if someone stuck a factory case in the chamber, it was tight closing. This proved to be the best method of all for handling belted magnums cases and in particular the Ackley Improved variety with their almost straight bodies and their 40 degree shoulders which made for more precise headspacing and phenominal accuracy. Now 20+ years later, we see a new breed of beltless magnum calibers flooding the market... What took so long?

I am happy to see the trend move away from belted brass. Gun builders and shooters will at last have some serious calibers in nonbelted form, that can be headspaced for optimum accuracy by conventional methods. I can't wait to see what's next...

Malm

I think the "field" gage is longer than the NO-GO gage, which is longer than the GO gage.

In the military, before a rifle was issued, headspace had to be between GO and NO-GO (chamber a GO, not chamber a NO-GO). Once the rifle was fielded (and shot) for a while, it was not sent back to the armorer until it closed on the longer "FIELD" gage. If it did not close on the "field" gage, it remained in service.

Go to www.brownells.com , search item number 319-308-630 and see for yourself.

Bill

To Paul H:

I AM DEFINITELY NOT, REPEAT, NOT CONFUSED ABOUT THE GO-NO GO-FIELD GAUGES AND THEIR RESPECTIVE LENGTHS. The thread that I so facetiously referred to was written by an idiot that thought the no-go was shorter, read shorter, than the go gauge. Jesus guys read that stuff and try to assimilate what is said. This is really getting out of hand so I quit and won't read this anymore.