Headspace Guage Question

G

Goldy

New member
Headspace Guage Question

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Help. I'm snowed in for a couple of days and decided to work on a project rifle. My problem is I need to check head space on this 30-06 before anymore stock work.

I can't find my no-go guage , just the go guage. Does any one know how much of a shim I would need to add to the go-guage to equal a no-go guage? I have plenty of shim stock, just can't find specs.

Thanks. ,,,goldy
 
Per what is registered with SAAMI, the 30-06 Springfield chamber shoulder, where it is .375" diameter, should be between 2.0487" and 2.0587" from the breech face.

The go gauge is going to be a hair over the minimum.

The 3M masking tape is typically .005" per layer, but there is some thin stuff out there, so you must measure it.

What does it all mean?
2 layers of masking tape for a no go.
 
Clark;

Thanks bunches. I tried 0.010 and it won't close so I'm good to go. Now I got something to do besides shovel snow.:D
 
I am pleased no one mentioned 'datum line' without it the answer is easy to understand.



If you add a .010 feeler gage to a go gage and the bolt closes on both the gage and the shim, you have .015 thousands head space. I am just guessing but you choose to use a .010 shim, that leaves me to assume you do not have the companion tool to the press the machinist feeler gage set, it starts at .001 and goes to beyond infinity.



If you cut a .005 shim from the gage and added it to the go-gage and placed both in the chamber, then found the bolt would close the chamber would be considered beyond no go-gage size, meaning the go-gage is +.005 longer than the minimum length chamber, I shoot ammo not gages so it is important for me to know how my ammo fits the chamber.



When my press, die and shell holder is adjusted to .000 plus 1/8 turn (.008) cases I size are full length sized, or equal in length from the head of the case to the shoulder as commercial ammo. Full length (minimum length) cases are considered .000 or .005 thousands shorter in length from the head of the case to it's shoulder than the chamber is from the bolt face to the shoulder of the chamber (in the perfect world) that is the reason I find (MOST)head space gages useless, I shoot ammo, I use ammo that is going to be fired in my chambers to test head space, in thousands.



So, when you add .010 thousand to a go-gage, place both in a chamber and the bolt does not close you know you have less than .015 head space, or if the bolt did close it could be said you have a chamber that is no go-gage length chamber + .001 thousands, again I have an M1917 with .016 head space, not a problem, I reload and form cases before I fire, not after.

Not because it is the cheap way but cutting shims from a feeler gage would in thousands would allow you to determine head space, as opposed to purchasing 3 gages for $60.00 plus, again, I do not shoot gages, I do not live in the perfect world, and, my press, shell holder and die is adjustable.

F. Guffey
 
"it could be said you have a chamber that is no go-gage length chamber + .001 thousands, again I have an M1917 with .016 head space, not a problem, I reload and form cases before I fire, not after......."

Somewhere in there is should have read it could be said you have a chamber that is field reject length + .001 thousands, or a no go-gage length chamber + .005.

Sorry about that.

F. Guffey
 
headspace!

Sir;
I NEVER, NEVER use a no go guage on a rifle that I set up. I headspace so that when barrel is screwed up that the bolt just BARELY closes on the go guage with no pressure and that there is ZERO play then!
Normal tolerance "from" the go guage would be a .006 shim on the go guage for rimless bottleneck cases. But I never use this. Also, on belted magnums I always, always, headspace with a .220 go guage! There should be NO play there. Now, SAAMI allows.007 from the go guage for the belted magnum case. Some Weatherbys, and others are .250 go.
In the belted magnum case with maximum headspace and a minimum case you can have .015 headspace - never do that! Always headspace on the go guage with NO play there!
Harry B.
 
Probably a dumb question, but how do you establish there's no play once the bolt is closed?
Click to expand...

Well you have to strip the bolt for one thing. No spring loaded ejectors, no spring loaded extractors, no firing pin, no firing pin spring, and remove claw extractors.

Put your Go gage into the chamber, lower the bolt. Push on the back of the bolt. If it does not move forward, you have a minimum chamber.
 
If you are addressing me as SIR, thank you, there is not one answer, that is the reason when starting I say I DO NOT KNOW, but it is very limiting when head space is go, no, or reject. on a 30/06 the numbers would be .000, +.005, + .009 and +.014, for that reason I do not use go, no or beyond gages, I want 14 options, when checking/chambering a barrel I want 12 options going the other way as in starting with -.012 below a minim length case to .000 to +.014.

If a barrel is screwed in with the go-gage chambered and the bolt has felt closing the head space reading is .005 thousands (for most re-loaders), the reason: The factory case is 'minimum length' or full length sized, the value when determining head space is .000, that value is placed on the length of the case from the head of the case to it's shoulder when compared to a go-gage. The go-gage is .005 longer from the head of the gage to it's shoulder than the minimum length case from the head of the case to it's shoulder.

The difference? There are new chambers, then there are chambers that have been in existence for 100 + years (again) I have an Enfield M 1917 Eddystone with .016 thousands head space (this is not the only one in existence), I form cases, my press, die and shell holder is adjustable with the companion tool to the press (feeler gage), I shoot this rifle with .000 head space with cases that are +.015 over .000, or cases that are 1.498 + .015 thousands from the head of the case to it's shoulder.

When reaming a chamber I do not use a go-gage (period), I do not shoot gages, I shoot minimum length ammo, if it fits the bolt will not close on a go-gage.

Stripping a bolt, I am not lazy, it is not required and pushing the bolt forward is a very hit and or miss method/technique. The P 14/M1917 Enfield bolt handle sets in a slot at the rear of the receiver, old Chilean Mausers use the bolt handle as a third safety lug etc., etc..

Then there is the 03 and 03A3, head space can be checked with nothing more than the ammo to be shot in the chamber and the companion tool to the press, the feeler gage, head space can is checked (by very, very, very few people) in thousands, cost of a feeler gage $11.00, a set of no, go and reject gages $70.00, and a go-gage can be modified to check head space from .005 to infinity, that would be a practical .016 thousands over a minimum length case.

Chambering a M1917 can be done without a go-gage, but I am not sure anyone is convinced the head space on an 03 can be measured more accurately with a feeler gage and If Springfield and or J. Hatcher had noticed the head space could have been a perminent part of the history of the rifle, the progression of head space could have been tracked by time and or number of rounds fired, in the beginning 03's did not stretch, there was nothing, then all of a sudden, but there was ware.

F. Guffey
 
I would get the FIELD gauge

When I mount a barrel and I have stripped the bolt, I want the bolt to close on the go gauge, but not the field gauge.
one simple way that woks for me, is taking small amount of foil and place layers of it inside the bolt face. when the bolt handle gets hard to close then I will mesure the Total thicness of the foil shims. Acording to SAMMI its ok to close on a no go gauge. It also says it is not OK to close on a FIELD GAUGE.
I dont use a no go gauge that much.
Ed
 
NO-GO gauge should not be closed on freely when the chamber is newly cut. The FIELD NO-GO gauge is to allow for some shooting-in of bolt lug fit and toolmarks and whatnot, and is therefore normally only applicable to checking a used gun. The GO gauge might better be called the MUST-GO gauge, as the chamber is too short if you cannot close on it without interference.

I do what Harry does. Match chamber pull-through reamers also set headspace correctly, but you have to stop and clear off chips and re-lube them constantly. You have to learn how they feel when they are cutting well and when they are packed with chips to avoid chamber scoring. Through-bore lubrication makes life much easier in that regard, when you can manage it.

Hatcher's Notebook has a section on headspace that is still worth reading. The leverage of the bolt handle can easily stretch a chamber with a gauge, forcing it to fit when it should not. Even crushing a foil gauge can do that if you aren't practiced and extremely careful. Lead foil like old-fashioned tinsel is better. Platigage may be best? Delicate touch serves well in this instance.
 
The factory case is 'minimum length' or full length sized, the value when determining head space is .000, that value is placed on the length of the case from the head of the case to it's shoulder when compared to a go-gage. The go-gage is .005 longer from the head of the gage to it's shoulder than the minimum length case from the head of the case to it's shoulder.
Click to expand...

Guffey, this is testable. You are saying that factory ammo is 5 thousands less than a minimum chamber. This will be interesting to find out. I am going to have to find some factory 30-06 and measure the stuff, with my Wilson gages.

When reaming a chamber I do not use a go-gage (period), I do not shoot gages, I shoot minimum length ammo, if it fits the bolt will not close on a go-gage.
Click to expand...

What do you use to set the headspace? A factory cartridge?

Stripping a bolt, I am not lazy, it is not required and pushing the bolt forward is a very hit and or miss method/technique.
Click to expand...

There are a lot of bolts that have spring loaded ejectors. When I am gaging for headspace I want to feel the slightest resistance to bolt closure. Especially as the powerful cocking cams on a bolt rifle will reduce the sensitivity.
 
You left the part out where I said I could convert a go-gage to a go to infinity gage, as opposed to purchasing a set of three gages for $60.00 + or - a few and even after purchasing three gages after using can only say the gage chambered or did not chamber, the smith and or reloader does not know how much head space the chamber has.Meaning if the go gage chambers, the chamber could have .009 thousands head space, for me head space is not something that is nice to know, I determine head space first in thousands.

I also make a gage that determines the effect a case will have on head space, new R-P box of 20 rounds will be to either side of .000 .00075, or a total of .0015 thousands.

The Wilson case gage is an excellent tool, it is even better if it is used with set-up table and or straight edge with the companion tool to the press, the feeler gage ('feeler gage': a tool foreign to smiths and reloaders).

Again I do not shoot gages

I was at the Dallas Market Hall gun show when I found a box of what appeared to be junk, I looked at the contents of the box and said DATUMS!!!, the vendor selling the items ask me "What does a datum look like" other comments, "where" ? and the funny one "I don't see one" I paid $5.00 for everything in the box, I did not need them but 'datums' come in handy.


I do not have a bolt handle like the one Hatcher used, 3 inches is about it, 20 pounds of weight at the end of a one foot wrench is 20 foot pounds, with a wrench that is 3 inches in length to get the same torque/effort 80 pounds must be applied, I under stand there is bolt advance and degree of rotation + the torque, the caming effect is nothing like fine threads, I wonder just how hard headed someone would be to apply enough pressure to stretch a receiver, and we need to determine where he found a receiver that would stretch, the LN receivers were 'nothing then all of a sudden' it was lying in a heap, or worst yes, someone had to recover the parts, those rifles did not take to stretching.

I do like the one where he moved the shoulder forward .125 thousands thinking the case would separate, instead he discovered head spacing on the extractor and designed his own chamber, the 30/06 + .125 modified Hatcher (same as the 8mm06 +.003 when comparing the 8mm57 to the 8mm06), he did use new cases, not cases that had been fired 5 times so they would be fully grown.

I do not get into mortal combat with the bolt, again I make gages from - .017 shorter than a go-gage to + .010 longer than a go-gage. The short bolt handle gives me a good feel for an interference fit.

F. Guffey
 
"Guffey, this is testable. You are saying that factory ammo is 5 thousands less than a minimum chamber. This will be interesting to find out. I am going to have to find some factory 30-06 and measure the stuff, with my Wilson gages"

When I find factory 30/06 ammo it always belong to someone else, when I want factory length ammo (minimum length) I full length size a case in a press that is adjusted to full length size a case, again I can measure the length of a case from the head of the case to it's shoulder, I can measure the length of a chamber from the bolt face to the shoulder of the chamber, I can tell you if the case will chamber before it is chambered.

When looking for factory ammo and 30/06 is not available I ask to 270 Winchester (new ammo) if that is not available, I ask for 25/06 (new ammo), for test purpose the length of all three from the head of the case to it's shoulder is the same (minimum/full length sized) and the go-gage for testing?? is the same gage for all three.

The minimum length was the case length from the head of the case to it's shoulder.
The chamber was refereed to as being go-gage length or .005 longer from the face of the bolt to the shoulder of the chamber than the length of the full length case (head of case to shoulder).

F. Guffey
 
30.06 Headspace

I believe the gentleman said he wanted to check an existing headspace, not a new cut one. I only breezed over the discussion, but it seems all of you are only half correct. I have used some pretty unconventional headspace checks when cutting new chambers, so I will leave that alone. The part about the datum line is only half true. I started out smithing in the military and 30.06 chambers are called off the top of the shoulder. Same with .308. That is why the newer reload books now usually have their own section, I am guessing. Military chambers and brass are not dimensioned the same. when you shoot civilian brass in 1917's,98 Krags, and others, the brass really balloons.
 
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When in doubt. . .GET THE PRINT

BEHOLD:

Picture001.jpg



Now, strip your bolt of anything associated with a spring and plop it into the receiver with a GO gauge. The bolt should rotate into battery under the force of gravity.

Now start cutting little postage stamps of shim stock and stick em to your bolt face with a dab of grease. Keep adding them until the bolt won't fall under the force of gravity.

Assume you used .004" worth of shim stock. The value would be "GO+.004" Your inside the maximum (generally around .006") so put it back together and go enjoy your gun.

IF it exceeds this value don't freak out, especially if your a hand loader. Seat your bullets long enough to ensure your case heads are firmly squashed up against the bolt face. Go shoot em. Now be a little conservative with your dies. Don't squish the case back to the spec case length. Just do enough to facilitate the action running smooth. Now reload and save these cases for this particular gun. All you've done is ensure that further case growth/movement is mitigated by pushing the shoulder forward instead of the web backwards. This is nothing more than fireforming just as you'd do for an Ackley cartridge.



I've been building rifles as a career (and now as a business owner) since 1999. I've yet to blow a gun up, be sued, or have one single problem.

Good luck.

Chad
 
Longrifles Inc.

I agree with what you say, your print is to SAAMI specs. I'm just saying if you fool around with older military chambers and after market gages, you could get into trouble. If you look on your print and the SAAMI print, they both call a point on the shoulder. Military chambers are called off the intersection of the shoulder and the body. Even the brass has different specs. Its easy to check headspace on a new cut, but can get dicey with something put together already.
 
Gunplummer is correct. I have a copy of the Garand blueprints and the chamber is specified as 1.282" from the barrel shoulder to the wider corner of the case shoulder counterpart in the chamber. The length of the shoulder to its intersection with the neck is not given, as the geometry of the shoulder angle and chamber neck diameters make that determination. Instead, lengths to throat and freebore and so on are given with a note as to the assumed diameter for which that length is valid. That diameter has a tolerance of +0.002", which alters those lengths when not right at the referenced minimum.

That Garand chamber and barrel thread blueprint does not specify where the bolt face would be? The bolt and chamber drawings taken together fix that dimension and the headspace tolerance. The Garand drawing is only concerned with defining a Garand barrel such that its chamber and thread timing and gas cylinder spline will make it interchangeable with all other Garand barrels without individual chamber reaming touch-up when installing it.

That is something SAAMI cannot do because SAAMI doesn't know what gun you might be putting the cartridge in? The case shoulder to barrel shoulder in a Mauser 98 action, for example, will be different than for the Garand, and so the Garand drawing is useless for figuring a .30-06 chamber for the 98. SAAMI has to specify the cartridge and chamber in a generalized way for use in all rifles, where the military drawings and gauges are concerned only with one model gun at a time.

The way SAAMI standardizes rounds is by making the manufacturer who introduces them responsible for providing the drawings and the proof loads and reference loads for that cartridge. When they have a round that was not a commercial round originally, such as military developments, or for which the original manufacturer is no longer in business, they assign responsibility to one of the existing ammunition manufacturers by agreement. That manufacturer then becomes responsible for supplying the specification and proof and reference loads to the industry.

As a result, the .30-06, like the .30-40 Krag and the .45-70, will have been put into SAAMI drawing format after the fact of the original military cartridge specifications. The new format drawings will be done so as to allow gun makers to chamber for those cartridges in different gun models. You can be sure, however, and most especially because so many military rifles chambered for .30-06 were later sporterized and used so much surplus ammunition, that following the SAAMI headspace method will provide a chamber that works with military ball ammunition, and that using a SAAMI headspace gauge will allow you to ream a chamber in a Garand or Springfield '03 variant that, when subjected to the military gauge set for the gun, will pass inspection.

One place SAAMI commercial specs and gauges fail to exactly replicate military chamber specifications is for the chamber tolerance differences in the 7.62 and 5.56 NATO rounds. You need a reamer with a longer throat and different length NO-GO and FIELD NO-GO gauges to match the military chambers for those rounds, but you can buy these. I am unaware of others.
 
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I didn't mean to get anybody all wound up, just tossing some facts out as"good to know" info. I remember someone bringing in a 1917 Enfield years ago, and a handful of brass that was really expanded. The owner thought the headspace was bad. He used Winchester brass, which normally runs on the low side of ammo size specs. The chamber was on the high (MIL specs). I would not have tried reloading that brass, it was so distorted. .308 chambers are worse and I believe there were warnings of this over the years. Anyway, you can get into trouble using SAAMI spec gages in MIL spec chambers, if the wrong combination is there. I may some of the info in the attic, I'm not sure. I have health issues and don't do much gun work anymore.
 
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