Head Spacing test?
- Thread starter trekstor
- Start date
sounds good. I guess I will wait for him to get back from his hunting trip.
Hungry here: I'm just out the back 40 hunting coyotes (they hear me coming and laughing) and I'm not far away. Send me a PM and I'll get you the instructions. Really easy. Most of the Norc's and Poly M14's I've measured are around 10 thou. The USGI M14's I used to own and compete with were hovering around the 15 thou (no joking) chamber dimension. NATO No-Go is 25 thou (near machine gun dimensions).
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The Wizard
CGN Regular
- Location
- Colorado Springs, Colorado USA
There is no right way to do the wrong thing! The PROPER way to measure headspace is with headspace gages. At the minium you need a GO and NO GO gages. Depending on the rifle the method to measure headspace varies. You know GOOGLE is your friend. Just GOOGLE "headspace" and you will find what you are looking for.
Hungry here: I've got all the gauges from Forster... they will drop in and be swallowed up. Then when your Norc bolt closes on a 1.630" GO gauge One might assume their #### will fall off and that's when all the panic starts. These are battle rifles, if any gauges should be used, the NATO gauges are the ones you (avoid buying them) need. Just mail me your brass. Of course the chamber will be large. That's a battle chamber for ya... Jean C. Garand designed his boomsticks to fire when the ammo is wet, cold , tired, hungry, pissed off, corroded, far from home, old, crusty, and muddy!
Hungry here: I've got all the gauges from Forster... they will drop in and be swallowed up. Then when your Norc bolt closes on a 1.630" GO gauge
One might assume their #### will fall off and that's when all the panic starts. These are battle rifles, if any gauges should be used, the NATO gauges are the ones you (avoid buying them) need. Just mail me your brass. Of course the chamber will be large. That's a battle chamber for ya... Jean C. Garand designed his boomsticks to fire when the ammo is wet, cold , tired, hungry, pissed off, corroded, far from home, old, crusty, and muddy!
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You make a good point, but if you take commercial brass that has never been fired and measure it, and it comes out with like .010 of stretch, you can start to think something might not be right.
autocrash
CGN Regular
I was wondering this too...
Although Hungry has graciously offered to measure fired brass, I'm interested in knowing how to do it myself.
I know it is not 100% correct to measure headspace from the brass, but as far as a quick check without disassembling the bolt it seems like a good idea.
Now I have a digital caliper (not the most accurate thing in the world, but pretty good...) but whats the trick for measuring the headspace?
Just looked at the SAAMI drawings, it looks like the headspace is measured at exactly half way up the shoulder, so if you measure the length at the neck (top of shoulder) and the body (bottom of shoulder) and divide by two, you should get the headspace... is this what Hungry is doing?
Hungry here: Nah, don't worry yourself. I use an RCBS Precision Mic ($ 80ish) for a .308 Win case. Don't waste your money. I've done it for you. Just send the 3 cases to me.
Matt
Although Hungry has graciously offered to measure fired brass, I'm interested in knowing how to do it myself.
I know it is not 100% correct to measure headspace from the brass, but as far as a quick check without disassembling the bolt it seems like a good idea.
Now I have a digital caliper (not the most accurate thing in the world, but pretty good...) but whats the trick for measuring the headspace?
Just looked at the SAAMI drawings, it looks like the headspace is measured at exactly half way up the shoulder, so if you measure the length at the neck (top of shoulder) and the body (bottom of shoulder) and divide by two, you should get the headspace... is this what Hungry is doing?
Hungry here: Nah, don't worry yourself. I use an RCBS Precision Mic ($ 80ish) for a .308 Win case. Don't waste your money. I've done it for you. Just send the 3 cases to me.
Matt
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Head space gauges. Measuring the brass only tells you how long the brass is. Brass has some "spring back" so you can chamber and extract without it sticking. Understand what you are trying to do, and read up on measuring head space, then get the gauges or get to someone who has them. It is the only reliable way to do it.
- Location
- Thunder |Bay
You can measure the headspace within .001 on YOUR rifle like this:
Chamber an unloaded and full length sized case in your rifle. SAMMI specs say that up to .006" is acceptable for the distance from the case head to your bolt face. Cut some pieces of shim stock (brass or stainless is OK) the size of your bolt face. Cut some at .001, .002. ,003. You can stick them to your bolt face with a little grease or bullet lube. Close the bolt with the shim stock until you can just feel the bolt meet some resistance as it reaches the end of its closing stroke. Remove the bolt and measure the size of the shim stock with a micrometer or even a good dial caliper. That is your headspace. You can stack the shims to get different thicknesses. If you shoot factory ammo, pull the bullet, empty the powder, and do the same thing.
It's a good idea to use unprimed cases for this. A high primer can throw all your measurements out of whack.
Contrary to popular belief, different factory rounds and different sizing dies will produce different amounts of headspace, usually within .002 or so. But if you have a chamber that is at the max allowable limit for headspace and you chamber a case with short headspace, you could wind up with a headspace of over .006 and still not be able to chamber a no-go guage!
If you find that the headspace for your rifle with the ammo you shoot produces headspace of .006, you will get case head separations after four or five firings if you always full length size. (5X.006=.030) You can adjust your sizing die to give you .001 headspace or less, and forget all about case stretching.
For John Q. Shooter, there needs to be a little headspace to allow grimy cartridges to chamber. If you are a reloader and particular about cleanliness of your cartridges and firearms, you can adjust to .0005 headspace. It will give you better accuracy (cases will be more concentric with the chamber when chambered), and reduce case stretching to almost nothing.
All a no-go guage tells you is that your chamber is within factory SAMMI specs.
Just my .02.
Rick.
ps. I'm in Thunder Bay. If you have any questions, send me a pm.
Chamber an unloaded and full length sized case in your rifle. SAMMI specs say that up to .006" is acceptable for the distance from the case head to your bolt face. Cut some pieces of shim stock (brass or stainless is OK) the size of your bolt face. Cut some at .001, .002. ,003. You can stick them to your bolt face with a little grease or bullet lube. Close the bolt with the shim stock until you can just feel the bolt meet some resistance as it reaches the end of its closing stroke. Remove the bolt and measure the size of the shim stock with a micrometer or even a good dial caliper. That is your headspace. You can stack the shims to get different thicknesses. If you shoot factory ammo, pull the bullet, empty the powder, and do the same thing.
It's a good idea to use unprimed cases for this. A high primer can throw all your measurements out of whack.
Contrary to popular belief, different factory rounds and different sizing dies will produce different amounts of headspace, usually within .002 or so. But if you have a chamber that is at the max allowable limit for headspace and you chamber a case with short headspace, you could wind up with a headspace of over .006 and still not be able to chamber a no-go guage!
If you find that the headspace for your rifle with the ammo you shoot produces headspace of .006, you will get case head separations after four or five firings if you always full length size. (5X.006=.030) You can adjust your sizing die to give you .001 headspace or less, and forget all about case stretching.
For John Q. Shooter, there needs to be a little headspace to allow grimy cartridges to chamber. If you are a reloader and particular about cleanliness of your cartridges and firearms, you can adjust to .0005 headspace. It will give you better accuracy (cases will be more concentric with the chamber when chambered), and reduce case stretching to almost nothing.
All a no-go guage tells you is that your chamber is within factory SAMMI specs.
Just my .02.
Rick.
ps. I'm in Thunder Bay. If you have any questions, send me a pm.
Will the ejector cause some resistance when closing the bolt? I thought you normally measured headspace with the bolt disassembled for this reason.
Some more usefull tools are a cartridge headspace comparitor and the redding competition shellholder set.
Then you can measure the headspace on your unfired, fired and resized brass and use the competition shellholders to adjust the amount the shoulder is bumped back when resizing.
If you fire a few cases with the gas system turned off then you will eliminate any stretch from the semi auto action when measuring fired brass for headspace. This can be an issue for the m14 style actions due to their somewhat voilent extraction.
Some more usefull tools are a cartridge headspace comparitor and the redding competition shellholder set.
Then you can measure the headspace on your unfired, fired and resized brass and use the competition shellholders to adjust the amount the shoulder is bumped back when resizing.
If you fire a few cases with the gas system turned off then you will eliminate any stretch from the semi auto action when measuring fired brass for headspace. This can be an issue for the m14 style actions due to their somewhat voilent extraction.
At the Victoria M14 seminar today,
we measured the head space on six Chinese M14 rifles.
FIRST,
WE CHECKED THE WEAR PATTERN ON BOTH BOLT LUGS,
to confirm that indeed both of THE BOLT LUGS were actually touching the receiver lugs [ which, believe me is NOT always the case ].
THEN,
We used a proper military issue 7.62 NATO GO Gage,
WHICH IS CUT OUT TO AVOID THE EXTRACTOR SPRING PRESSURE.
and a set of automotive feeler gages,
to measure the space at the right lug.
IF and only IF,
the wear pattern shows even wear on both bolt lugs,
you can extrapolate that the bolt is sitting square to the chamber,
and that head space is exactly what the feeler gage reads at the right lug.
Ok fine,
almost all of the as new M14 Norcs and Polys read about .006" - .008" over the Go gage,
which is EXCELLENT!! I've seen measurements on brand new M305s go as high as .017".
All of these rifles should be safe to shoot with BOTH 7.62 NATO ammo, and with .308 WIN ammo.
One of Brobee's M14 shorty builds,
with a hand lapped TRW bolt,
not surprisingly,
read dead on the GO gage.
This M14 shorty had a Criterian barrel, an excellent trigger job, and showed quality workmanship and parts all the way.
SURPRISINGLY,
my personal near new Norc also read dead on the GO gage.
OOPS,
how embarrassing!!!
[;{(
This serendipitous surprise was because we accidentally used my spare Norc demo bolt
[after stripping and assembling a demo bolt to show the internal bits, we put the spare/demo bolt on the table next to my gun.]
When we checked agin with the proper serial number matching bolt,
we got the usual .006" thou
SO,
I now will be lapping in that spare bolt to get perfect bearing AND a few thou over GO.
Serendipity is some times a good thing, BUT,
NOT ALL M14 BOLT SWAPS WORK OUT THIS WELL!!!
[;{)
LAZ 1
.
we measured the head space on six Chinese M14 rifles.
FIRST,
WE CHECKED THE WEAR PATTERN ON BOTH BOLT LUGS,
to confirm that indeed both of THE BOLT LUGS were actually touching the receiver lugs [ which, believe me is NOT always the case ].
THEN,
We used a proper military issue 7.62 NATO GO Gage,
WHICH IS CUT OUT TO AVOID THE EXTRACTOR SPRING PRESSURE.
and a set of automotive feeler gages,
to measure the space at the right lug.
IF and only IF,
the wear pattern shows even wear on both bolt lugs,
you can extrapolate that the bolt is sitting square to the chamber,
and that head space is exactly what the feeler gage reads at the right lug.
Ok fine,
almost all of the as new M14 Norcs and Polys read about .006" - .008" over the Go gage,
which is EXCELLENT!! I've seen measurements on brand new M305s go as high as .017".
All of these rifles should be safe to shoot with BOTH 7.62 NATO ammo, and with .308 WIN ammo.
One of Brobee's M14 shorty builds,
with a hand lapped TRW bolt,
not surprisingly,
read dead on the GO gage.
This M14 shorty had a Criterian barrel, an excellent trigger job, and showed quality workmanship and parts all the way.
SURPRISINGLY,
my personal near new Norc also read dead on the GO gage.
OOPS,
how embarrassing!!!
[;{(
This serendipitous surprise was because we accidentally used my spare Norc demo bolt
[after stripping and assembling a demo bolt to show the internal bits, we put the spare/demo bolt on the table next to my gun.]
When we checked agin with the proper serial number matching bolt,
we got the usual .006" thou
SO,
I now will be lapping in that spare bolt to get perfect bearing AND a few thou over GO.
Serendipity is some times a good thing, BUT,
NOT ALL M14 BOLT SWAPS WORK OUT THIS WELL!!!
[;{)
LAZ 1
.
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- Location
- Thunder |Bay
You are correct. Remove the ejector.
- Location
- Steel Town
Has anybody tested the headspacing on the 2009 batch of Polytechs yet?
The 7.62 NATO MATCH gages I used were made for building MATCH US GI M14s, to be used ONLY for TARGET competition.
Therefore, my 7.62 NATO GO is less than the military armourer's usual standard 7.62 NATO GO gage. For rack grade M-14 rifles military specs call for:
7.62 NATO GO = 1.6355” [ very close to .308 NO GO ]
The 7.62 NATO MATCH GO gage I used is marked: 1.6315" MIN.
1.632" is the IDEAL dimension that I aim for when lapping in a bolt in an M14 which will be used with BOTH .308 Win ammo, and 7.62 NATO BALL ammo. This would also be the ideal dimension for an M14 that will be used for hunting or field use, and possibly not cleaned every single time it is shot.
For M14 rifles intended ONLY for the target range, which will be cleaned with pathological retentiveness, after every range session, and used almost exclusively with .308 WIN MATCH ammo, I set the head space to .308 WIN GO, or 1.630".
Hope this clarifies the head space numbers THEORETICAL game,
but,
as an executive summarry,
IN REALTY,
decades of experience here in Canada with thousands of Chinese M14 rifles has pretty well proven that,
IF YOU USE FACTORY AMMO in your M14,
EITHER .308 WIN OR MILITARY BALL,
you are more likely to get into trouble with a chamber that is head spaced too short,
than one of the commonly found Chinese M14s that are marked as .308 WIN on the receiver, but in reality ALMOST ALWAYS HAVE 7.62 NATO head space measurements ... AND SOMETIMES EVEN AT THE HIGH END OF THE HEAD SPACE RANGE.
BTDT,
this is my personal opinion based on building and shooting hundreds of M14 type rifles, over 25 years.
Of course,
any opinions you get for free on the internet may be worthn much less than you paid for them,
and
YPMMV
LAZ 1
[;{)
Therefore, my 7.62 NATO GO is less than the military armourer's usual standard 7.62 NATO GO gage. For rack grade M-14 rifles military specs call for:
7.62 NATO GO = 1.6355” [ very close to .308 NO GO ]
The 7.62 NATO MATCH GO gage I used is marked: 1.6315" MIN.
1.632" is the IDEAL dimension that I aim for when lapping in a bolt in an M14 which will be used with BOTH .308 Win ammo, and 7.62 NATO BALL ammo. This would also be the ideal dimension for an M14 that will be used for hunting or field use, and possibly not cleaned every single time it is shot.
For M14 rifles intended ONLY for the target range, which will be cleaned with pathological retentiveness, after every range session, and used almost exclusively with .308 WIN MATCH ammo, I set the head space to .308 WIN GO, or 1.630".
Hope this clarifies the head space numbers THEORETICAL game,
but,
as an executive summarry,
IN REALTY,
decades of experience here in Canada with thousands of Chinese M14 rifles has pretty well proven that,
IF YOU USE FACTORY AMMO in your M14,
EITHER .308 WIN OR MILITARY BALL,
you are more likely to get into trouble with a chamber that is head spaced too short,
than one of the commonly found Chinese M14s that are marked as .308 WIN on the receiver, but in reality ALMOST ALWAYS HAVE 7.62 NATO head space measurements ... AND SOMETIMES EVEN AT THE HIGH END OF THE HEAD SPACE RANGE.
BTDT,
this is my personal opinion based on building and shooting hundreds of M14 type rifles, over 25 years.
Of course,
any opinions you get for free on the internet may be worthn much less than you paid for them,
and
YPMMV
LAZ 1
[;{)
What about reloading for it though?
I have some IVI brass, once fired, that is stretched further than the new commerical .308 brass my m14 spits outs... so I'm going to have to full lenth resize, but with my headspace being so far out(on the dangerous side you said when you ran the gauges through my rifle) how many uses could I safely get out of military brass the way my rifle is? What is the most cost effective way to make this rifle safe to use with reloaded ammunition while replacing the least number of parts possible?
I intend to anneal my case necks, I'm guessing every 4-5 cycles, so I intend to use the brass until it can no longer be used, due to the age and wear from the number of cycles.
The first thing to say about reloading for the M14,
is that I have never, in 25 years, seen a DOCUMENTED, PROVEN case of an M14 excessive head space Kaboom that involved FACTORY AMMO.
However,
I have heard MANY stories about M14 blow ups , that ALL OCCURRED WITH RELOADS!!!!
SO,
reloading for the M14 [ or any other high powered semi auto rifle ] is definitely NOT for the beginner, the sloppy, the stupid, or the uninformed.
And in some of those categories, I may include my self.
[;{)
I rarely reload for the M14, although I have saved up a LOT of .308 Match brass, and 7.62 NATO brass, and am planning to get back into it soon.
When I did reload, I almost always used the thicker/stronger 7.62 NATO brass, mostly because it held up better after being abused in a semi auto rifle, and then thrown off on to a rock or a concrete shooting pad.
I loaded mostly either IVI [ which varied quite a bit in internal volume ]
or Lake City Match brass.
For my practice, practical match, and ZOMBI loads, I loaded 125 Gr SP bullets, roughly eqivalent to the Hornady TAP ammo, which was not available back then. Or else I used the BULK Lapua 123 GR FMJ .310" bullets, intended for the 7.62 X 39 Russian cartridge. And I loaded these at reduced velocities. The brass seemed like it would last indefinitely, as long as I stayed off of concrete shooting bays [ which beat the heck out of the ejected cases ].
As for MATCH grade target loads, I very rarely bothered reloading for accuracy, as I went through way too many M14s as I built them up for resale. For accuracy testing I had cases of 168 Gr HPBT match ammo from Federal and Winchester, and was more interested in what a newly built 14 would do with these standard loads, than in tailoring the best load for any individual rifle. These rifles did NOT stick around for long .... build them, test them, flog them ...
and try NOT to get emotionally attached to the inventory,
no matter how good it shot.
So what I am saying here is that I am definitely NOT the best person to ask about reloading for the M14.
There are several others posting on CGN who have much more experience at reloading for the M14 than I do .... maybe you should ask them.
[;{)
LAZ 1.
is that I have never, in 25 years, seen a DOCUMENTED, PROVEN case of an M14 excessive head space Kaboom that involved FACTORY AMMO.
However,
I have heard MANY stories about M14 blow ups , that ALL OCCURRED WITH RELOADS!!!!
SO,
reloading for the M14 [ or any other high powered semi auto rifle ] is definitely NOT for the beginner, the sloppy, the stupid, or the uninformed.
And in some of those categories, I may include my self.
[;{)
I rarely reload for the M14, although I have saved up a LOT of .308 Match brass, and 7.62 NATO brass, and am planning to get back into it soon.
When I did reload, I almost always used the thicker/stronger 7.62 NATO brass, mostly because it held up better after being abused in a semi auto rifle, and then thrown off on to a rock or a concrete shooting pad.
I loaded mostly either IVI [ which varied quite a bit in internal volume ]
or Lake City Match brass.
For my practice, practical match, and ZOMBI loads, I loaded 125 Gr SP bullets, roughly eqivalent to the Hornady TAP ammo, which was not available back then. Or else I used the BULK Lapua 123 GR FMJ .310" bullets, intended for the 7.62 X 39 Russian cartridge. And I loaded these at reduced velocities. The brass seemed like it would last indefinitely, as long as I stayed off of concrete shooting bays [ which beat the heck out of the ejected cases ].
As for MATCH grade target loads, I very rarely bothered reloading for accuracy, as I went through way too many M14s as I built them up for resale. For accuracy testing I had cases of 168 Gr HPBT match ammo from Federal and Winchester, and was more interested in what a newly built 14 would do with these standard loads, than in tailoring the best load for any individual rifle. These rifles did NOT stick around for long .... build them, test them, flog them ...
and try NOT to get emotionally attached to the inventory,
no matter how good it shot.
So what I am saying here is that I am definitely NOT the best person to ask about reloading for the M14.
There are several others posting on CGN who have much more experience at reloading for the M14 than I do .... maybe you should ask them.
[;{)
LAZ 1.
