Headspace question- check my work

B

BoogieMan

New member
I have plenty of machining experience and many times it comes down to feel on manual work and gages. I dont have a local schooled gunsmith to ask questions. I built a remage (savage style barrel on 700) and I have both go/no-go for my cartridge. Bolt closes with the slightest amount of pressure on the go. Will just start on the cam with the no-go. I checked my work against some PPU loaded ammo I have on hand. Requires light pressure to close the bolt on the ammo. Open up easily but the bolt requires a bit of a tap with my palm to slide open. This is a target gun not a hunting gun. Still I feel its a bit tight. I backed off approx 5 degrees (.0008) and the ammo sticks much less. I still have to open to the extraction cam on bolt handle or tap the bolt back. But, it closes with min pressure on a factory cartridge, fals closed on go gage. Lugs begin to engage cams but will not close on no-go.
Any flaw in my method? Any reason I should make any changes? If this were a hunting rifle I would likely loosen up another 5-10 deg.
 
Last edited:
It's generally not a good idea to use ammo or cases as a go gauge. Since there's a tolerance in SAAMI spec, there will be a tolerance in your results that may mean that one ammo functions as a Go Gauge but next time you buy Brand Y instead and it's a "No Go" guage. Oops.

Since you're custom building the gun, the actual spec is largely irrelevant. If you want it to be tight or lose on Go Gauge, that's fine. You could even make it close on the No Go, so long as you size your brass accordingly. It really doesn't matter.

But, if you don't use the Go Gauge then you'll have to be aware that any given ammo may or may not fit. If you make your own, it don't matter what the gauges say. Set the sizing die accordingly and roll it.
 
Brian it closes on the GO gage but sticks on factory ammo. Is that just this particular batch of ammo is running on the large end of spec? I am harvesting the factory brass during break in period then I will likely neck size only or use very little setback when sizing.
It is a custom rifle for my use. Still, if I ever decide to sell it I wouldnt want an issue for the next guy.
 
I saw that, it's a bit odd. I'm curious if it isn't some dimension other than head space/clearance. I assume this is a custom chambered barrel, possibly made with a near SAAMI minimum reamer?

Anyhow, so long as the bolt will close, actually firing the cartridge will solve the tightness issue.:p

Are the gauges rented or do you own them? If you own them, you can always reset the barrel if you ever decide to sell.
 
I have used a cartridge case many times to set headspace. Use a case that was already full length resized. I think the problem here is in the OP - -PPU ammo. European ammo manufacturers are not on the same wavelength we are.
 
Thanks for the review guys. I am going to install the jewel trigger and put the bolt back together. The No-Go will not close as its set. If I give the no go light pressure with one finger the lugs are beginning to engage. Bolt is about the 2 o'clock position. The PPU ammo is still a little tight on extraction. But, I will chalk that up to Euro ammo. I will resize it all after I get through break in and start to work up loads.
 
I cant believe how good and light the Jewel trigger is. I have several handguns and rifles that I considered to be excellent trigger pull. Wow. They dont even come close to the clean 1lb trigger.
 
"...not a good idea to use ammo or cases as a go gauge..." Or any kind of gauge. Empty cases and loaded ammo are not precise instruments like gauges are.
"...closes with the slightest amount of pressure on the Go..." Headspace is a tick short. Shouldn't be any resistance or pressure required. Any tool marks in the chamber?
 
Bolt closes with the slightest amount of pressure on the go. Will just start on the cam with the no-go. I checked my work against some PPU loaded ammo I have on hand. Requires light pressure to close the bolt on the ammo.
Click to expand...

And that does not make sense; if the chamber is go-gage length and the ammo is minimum length the bolt should close without effort on your new ammo. If I had loaded ammo and a head space gage I would compare the length of the gage from the shoulder to the head of the gage with the length of the ammo from the shoulder to the head of the case.

I understand how difficult that task can be for reloaders that have specs., standards and tolerances without a way to 'ZERO' their gages. I am the fan of standards and transfers.

F. Guffey
 
Where on the shoulder? European standards are not exactly the same as ours. I have seen many warnings stating not to use a GO and NO Go gage from two different manufacturers. There are a lot of variations involved. I once made a reamer to match the dies on an 8x57. Once the brass was fired once and trimmed, there was no brass movement from full length re-sizing. I fired some cases at least a dozen times. I did not see one bit of an increase in accuracy. I simply do not understand the "Must have water tight headspace mentality" that seems to be the norm now days. Headspace is not written in stone. There are just too many variables involved.
 
I still have to open to the extraction cam on bolt handle or tap the bolt back. But, it closes with min pressure on a factory cartridge, fals closed on go gage. Lugs begin to engage cams but will not close on no-go.
Any flaw in my method?
Click to expand...

Yes there is a flaw, had you used your PPU ammo (no mention of diameter, case length and diameter of the bullet) to adjust the length of the chamber you would be finished. If you had compared the length of your gage with the length of the ammo you would know why the bolt will not close on your ammo. There is go-gage length chambers that are used with minimum length/full length ammo. That only works when the reloader knows how to measure the length of the chamber from the shoulder to the bolt face and the length of the case from the shoulder of the case to the case head.

I do not have too many variations because I only use one standard and I start with zero.

F. Guffey
 
Do you want to know the difference in length between the go-gage, no go-gage and the ammo you are using in thousandths? Do you have a chambered barrel? Do you have a height gage, depth gage or a dial caliper?

I would drop the no go-gage into the chamber then measure the gage protrusion from the barrel and then I would write the measurement down and then go to the go-gage and place in into the chamber and measure the gage protrusion from the barrel and write the measurement down then subtract the small number from the large number to get the difference in length between the two gages.

And then; place one round of PPU’?’ ammo into the chamber and measure the case head protrusion from the barrel then record the measurement. Because of all the variations and other excuses I would suggest you measure the protrusion of at least 10 rounds being careful with the primers when working off of the case head. If the protrusion for your ammo is the same protrusion for your head space gage you need to shorten the length of the case from the shoulder to the case head or get a longer go-gage; The Savage jam nut barrel was suppose to make these task easier, and then everyone got consumed with variations, +/-eases and tolerances.

And someone needs to explain the: “I backed off approx 5 degrees (.0008)”, there are threads, fine threads and then there must be ‘mighty fine threads’.

F. Guffey
 
That is really a good way to check, if you are a lumber jack or something. What in the world makes you think the contact area on the case is the same as on the gage? Put ten cases in the barrel and see if you get the same reading on all of them. Factory loaded cases are all over the place on dimensions, that is why you get different lengths when you full length re-size. I have never had an 8x57 Mauser pass a NO GO SAMMI spec gage. Nothing wrong with them, their specs just a little different. A guy brought me a 1917 that he thought was expanding the brass way to much. He was using Winchester commercial brass (Notoriously known as the smallest spec brass of US manufacturers) and putting it in a MILSPEC chamber. Nothing wrong with the chamber. Again, different specs.
And by the way, T OHeir is correct. You do not apply pressure on the GO gage. You can damage the chamber.
 
A No-Go gauge only tells one that there is more headspace than Go, but that does not necessarily mean that they are unsafe. The No-Go shows a dimension toward the end of the safe range, but not necessarily unsafe. A field gauge is what tells if one is considered unsafe. Some chambers were designed to eat any commercial ammo, and do have a good bit of headspace when compared to the Go gauge dimension, especially military rifles. A Go gauge was designed to tell a smith when a chamber was finished to the minimum SAMMI dimensions. The bolt should easily close against a Go gauge without any force.

See the video at the link below, under the bottom of the photo on the LH side:

http://www.brownells.com/gunsmith-tools-supplies/measuring-tools/headspace-gauges/headspace-gauges-no-go-prod40876.aspx
 
I have never had an 8x57 Mauser pass a NO GO SAMMI spec gage.
Click to expand...

I have no fewer than 40 8mm57 take off barrels with small and large shanks, when checking the chamber lengths it is very rare to find case head protrusion from the barrel greater than .110". And then the person doing the measuring turns around and measured the receiver from the seating ring to the bolt face and it is rare for me to find one that does not measure .115" +/- very little. The .005" difference is clearance.

I purchased 4 complete Mausers for a wildcat build; when I purchased the rifles I paid $25.00 each with a caution, the receivers could be suspect. There was not .001" difference in the length of the chambers from the shoulder of the chamber to the bolt face. But the rifles had to be tested, I used one barrel for all 4 receivers with one bolt, the difference in length between all 4 was .0005"+/-.

F. Guffey
 
A guy brought me a 1917 that he thought was expanding the brass way to much. He was using Winchester commercial brass (Notoriously known as the smallest spec brass of US manufacturers) and putting it in a MILSPEC chamber. Nothing wrong with the chamber. Again, different specs.
Click to expand...

A guy? Another story that starts out with "A guy". You could not tell him the length of the chamber from the shoulder to the bolt face and then there is the diameter? I checked the length of the chamber in a M1917 and found the chamber was .002" longer than a field reject length gage, I did not knash my teeth or wring my hands because I did not find the long chamber unusual for the M1917. I formed 30/06 cases out of 280 Remington cases. I adjusted the 30/06 sizing die off the shell holder .014" and then sized the cases for the long chamber. Adjusting the die off the shell holder .014" automatically gave me the magic .002" clearance.

The 30/06 case minimum length/full length sized in the perfect world is .005" shorter than a go-gage length chamber. I added .011" to the length of the case from the shoulder to the case head. I know, some one has to be curious about the case length, when trimming I add the .014" to the trim length. I am the fan of cutting down on all that case travel. Then there are those that assume the case stretched between the case head and case body when fired and they have no way of knowing one way of the other.

I would have told 'That Guy' he should apply the leaver policy to his fired cases, after the case shoulder forms to the chamber leaver where he founder.


F. Guffey
 
Didn't read all the above, but these are my "rules"...

Gauges (go, no-go) must be from the same manufacturer. DO NOT mix a PTG "go" gauge and a Manson "no-go".

If shooting factory ammunition, .001- .0015 above "go" is the goal.

You're closing with slight resistance on the Prvi ammunition which indicates zero headspace. Nothing wrong with that...you're fine as long as you're not having to close the bolt with excessive force. You did remove the FP/spring/ejector I presume so there is no resistance felt when running the bolt with no gauge or case in the chamber.

If you were handloading- I would have suggested using the largest datum length cartridge from a number of them that have fireformed and run through your sizing die- and setting the headspace to zero based using that cartridge.
 
Gauges (go, no-go) must be from the same manufacturer. DO NOT mix a PTG "go" gauge and a Manson "no-go".

I can not imagine a reloader and or smith that can not measure the length of a go-gage no matter the manufacturer. I can not imagine a reloader and or smith that does not have the skill to compare the length of two different gages when deterring the difference.

A resource/collector/builder of Springfield 03 was building a Rock Island 03 correct for 1911. His bolt would close on a head space gage but not on a no go-gage; as some of us know that is OK for government work but he wanted a go-gage length chamber and was not happy he had 20 30/06 head space gages and none of them fit.

Anyhow I was buying a mill from him when he mentioned head space and the difficult he had dealing with reloading forums so I told him "this is your lucky day". I explained to him head space gages are nice but I do not shoot gages, I shoot ammo. I offered to modify one of his go-gages to a go-gage to infinity gage meaning it would measure the length of the chamber in thousands from go-gage length to a practical length of .015" longer than a go-gage length chamber.

Anyhow, I measured the length of his chamber, it was .0025" longer than a go-gage length chamber meaning when he fired a minimum length/full length sized case he would have .0075" clearance. The collector has no fewer than 100 Springfield bolts, I offered to go through his bolts in an effort to find one that would off set the length of the chamber, but; he had only one straight handle bolt and I promised him we would not find a bolt that would reduce the length of the chamber by .0025". I have 35 new replacement bolts for the 03A3 type rifle, again I do not have one that would reduce the length of his chamber by .0025"

Anyhow he received some straight handle bolts from John Beard, I was long gone by that time.

F. Guffey
 
I can not imagine a reloader and or smith that can not measure the length of a go-gage no matter the manufacturer.
Click to expand...

That was not my point. "Measuring" the exact length to the gauge datum is not so simple (but please enlighten me if you know something I do not) but can be done with reasonable accuracy with a comparator- but even that is not exact as these are not precision ground for extreme accuracy.

Point was, you will find small variations in these dimensions between manufacturers, so in the interest of consistency it is best to keep to the same one.

Brownell's makes the same point:

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.
Click to expand...

http://www.brownells.com/.aspx/lid=12555/GunTechdetail/Headspace-Gauges-And-How-To-Use-Them-Part-I
 
If these things are not consistent between brands, then they would be useless to me. Thank the powers that be for the fact that I have no use for them or I would be upset.
 
You must log in or register to reply here.
Back
Top