Check HeadSpace

[Gergify]

So I never checked the headspace on any rifle. I'm getting a Polytech M1a, so I'll have to check it. Now I know I need a head space field gauge, but I didn't realize I complicated it is to check it. I did know you have dissemble the whole gun.

Can anyone direct me to a site that gives good instructions and photos if this process (i'm a visual learner)? Is there any easier way to check the headspace?


Thanks

 

[Duke of Doubt]

What makes you think you have to check headspace?

Modern commercial headspace gauges are not manufactured to the same specifications and tolerances as factory original headspace gauges for vintage foreign military rifles. Accordingly, they will give you a measurement that actually doesn't mean much, but which appears to tell you whether the rifle is safe or not.

You'd be better off researching the rifle and inspecting it for signs of excessive or insufficient headspace, then test-firing from the hip or, if you are the timid sort, using the old tire and string method. Then inspect the brass for signs of excessive headspace, such as case neck splitting, backed out primers, etc. Do this several times. After a dozen or so shots, and probably fewer, you should either turn up any problems or gain confidence in your weapon.

 

[jim in Anchorage]

Old Tire and string method? I thought I invented that[just between us gals,it involved a certain "modification" of a SKS 20 years ago]

 

[Duke of Doubt]

jim-in-Anchorage: "Old Tire and string method? I thought I invented that ..."

I think Peter-Paul "Cyclops" Mauser invented it, the day after he took most of a rifle bolt into his right eye.

 

[jim in Anchorage]

Never heard the Mauser story. That would definitely hurt.

 

[Slamfire]

So I never checked the headspace on any rifle. I'm getting a Polytech M1a, so I'll have to check it. Now I know I need a head space field gauge, but I didn't realize I complicated it is to check it. I did know you have dissemble the whole gun.

Don't know a site.

You do not have to disassemble the whole gun. Take the action out of the stock, take the operating rod off, and remove the bolt. You do have to disassemble the bolt. You do not want any extractors, plungers, springs, spring tension, to fool or mislead you.

Once you have the disassembled bolt back in the rifle, and the operating rod is still off the rifle, you can place the rifle headspace Go gage in the chamber. You should be able to lower the bolt, using your fingers, without any resistance, on the go gage.

Shake the go gage out and put the "No Go" gage in the rifle. Now lower the bolt and gently, very gently, lower the bolt lugs into the locking recesses. You should feel a solid resistance before the bolt lugs go fully into battery. Don't force it.

If so, your rifle is fine and is within commercial specs.

However, US Military M14's (and maybe Polytech's) had a lot more headspace than commercial copies. You will have to search for the web site, but I have seen the Military headspace specs for the M14, and they are larger.

A Military friend of mine, inspected about 15 M14's that were fresh from the Anniston Army Depot. These rifles were being given to a unit going over to Kuwait, to shoot land mines. He said everyone of these military M14's swallowed the commercial field gage.

I believe there is something to this. I torqued a like new HRA barrel on a commercial SA receiver. The barreled action swallowed my field gage.

 

[lipadj46]

I would not take Don't Mr. Doubt's advice. Well do that too but first check the headspace and keep checking it after you shoot the first 10 times or so.

What makes you think you have to check headspace?

I'm assuming you are not into M14's because if you were you would know why he needs to check the headspace in a chinese M14. They have been rumored to have a soft bolt defect (like SAI did at one point but of course SAI had a recall Norinco and polytech did not) so it is a good thing to check to see if it needs a USGI bolt conversion.

To the OP you just put the headspace gauge in your chamber like a live round and close your bolt.

- On a No Go gauge if the bolt closes and locks up on the gauge then you have excessive headspace. If your bolt does not close all the way then you are good to go.

- On a Go gauge if the bolt closes and locks up on the gauge then you are good to go. If your bolt does not close all the way then you have too little headspace.

- If your rifle's action closes on the Field gauge the chamber is dangerously close to or over the specified maximum chamber size.

Your gauge should come with instructions.

Like the poster above mentioned a military 7.62 Nato rifle has a little more headspace than a commercial .308 so keep that in mind or try to find a 7.62 Nato only headspace gauge.

Here are gauges that are made specifically for 7.62 Nato (one is a little longer for deeper cut chambers).

http://www.e-gunparts.com/DisplayAd.asp?chrProductSKU=1084500&chrSuperSKU=&MC=

 

[Duke of Doubt]

lipadj46: "I'm assuming you are not into M14's because if you were you would know why he needs to check the headspace in a chinese M14. "

Nope, not into Chinese M14s. Why, are they built out of spec?

 

[lipadj46]

Nope, not into Chinese M14s. Why, are they built out of spec?

Some had bolts that were soft. Like SAI did but SAI did a recall and you could look at the serial number Norinco and Polytech never had a recall so you don't really know for sure.

 

[jim in Anchorage]

Soft bolts,excessive headspace-sure makes me want to run out and buy a Chi-Com rifle.

 

[lipadj46]

Soft bolts,excessive headspace-sure makes me want to run out and buy a Chi-Com rifle.

Well like I said SAI had a soft bolt issue and even the USGI bolts at times had issues with improper heat treating so it is not anything really against a Chi Com M14. They do have a the best hammer forged receivers available today (better than LRB even, dimensionally speaking) and have chrome lined barrels (SAI no longer offer this). So you get all this for $700 -$800 which is a deal and even if you have to replace the bolt and add say $500 to the price you are still in under a used SAI M1A with a cast receiver.

Anyways please do us a favor and don't buy one. Keep the prices low for those who know better

 

[jim in Anchorage]

Will do.

 

[dmazur]

I always get tangled on this, too -

- On a Go gauge if the bolt closes and locks up on the gauge then you are good to go. If your bolt does not close all the way then you have excessive headspace.

Well, if it won't close on the GO gauge, that's insufficient headspace. Factory ammo will prevent the bolt from closing.

(Get a gunsmith with a pull-thru reamer who knows how to use it, and ream it to correct headspace...much better than the excessive headspace issue. )

 

[Gergify]

So in theory, I only have to pop the field gauge into the chamber like a bullet and see if it closes over it?

Also I don't have the serial number, I forgot to write it down when I was looking at the polytech, I'll be receiving the gun tomorrow though so I can check on that.

I'm getting the Polytech M1a (as stated in my other thread) for $800. I'm getting five (5) 20rd magazines and 1000 rounds of surplus ammo with it as well. So a pretty good deal i guess.

 

[lipadj46]

Yes exactly. You want a No Go or Field Gauge to check for excessive headspace..

Get a gunsmith with a pull-thru reamer who knows how to use it, and ream it to correct headspace...much better than the excessive headspace issue.

The whole point of this is to guard against the possibility of a soft bolt. It has nothing to do with getting a smith to correct the headspace of the rifle. You need to check and make sure the bolt is not deforming and causing excessive headspace. So if you are good to go the first few times out you probably do not have a problem.

Well, if it won't close on the GO gauge, that's insufficient headspace. Factory ammo will prevent the bolt from closing.

Yes I missed tha in a copy an paste

 

[Gergify]

"Here are gauges that are made specifically for 7.62 Nato (one is a little longer for deeper cut chambers).

http://www.e-gunparts.com/DisplayAd....rSuperSKU=&MC="

So will I need the Min. or Max. chamber gauge?

 

[jerkface11]

You need the max gauge.

 

[Jeremy2171]

lipadj46 I would not take Don't Mr. Doubt's advice. Well do that too but first check the headspace and keep checking it after you shoot the first 10 times or so.


Quote:
What makes you think you have to check headspace?

I'm assuming you are not into M14's because if you were you would know why he needs to check the headspace in a chinese M14. They have been rumored to have a soft bolt defect (like SAI did at one point but of course SAI had a recall Norinco and polytech did not) so it is a good thing to check to see if it needs a USGI bolt conversion.

To the OP you just put the headspace gauge in your chamber like a live round and close your bolt.

- On a No Go gauge if the bolt closes and locks up on the gauge then you have excessive headspace. If your bolt does not close all the way then you are good to go.

- On a Go gauge if the bolt closes and locks up on the gauge then you are good to go. If your bolt does not close all the way then you have too little headspace.

- If your rifle's action closes on the Field gauge the chamber is dangerously close to or over the specified maximum chamber size.

Your gauge should come with instructions.

Like the poster above mentioned a military 7.62 Nato rifle has a little more headspace than a commercial .308 so keep that in mind or try to find a 7.62 Nato only headspace gauge.

Here are gauges that are made specifically for 7.62 Nato (one is a little longer for deeper cut chambers).

http://www.e-gunparts.com/DisplayAd....rSuperSKU=&MC=

Clarification:

GO gage- Your bolt MUST close on this otherwise the chamber is too small to safely chamber and fire a round. Can be corrected by swapping bolts or finish reaming.

NO GO- This is the max length for a NEW barrel. When installing a new barrel and you have to ream to set headspace you use both GO and NOGO to ensure you don't over ream to far. The ONLY reason to use this gage is when installing a NEW barrel.

FIELD- This gage is used to show when the max allowable headspace has been reached and the weapon should be inspected to confirm what repairs are needed. This is the only gage the military uses to determine if a weapon is safe to fire. "Max allowable chamber dimension".

 

[Owen]

If you poke around, you can find gages that can be used with the bolt assembled. They are relieved so the ejector and extractor don't touch the gage.

 

[TimRB]

At a minimum, you must remove the extractor and ejector from the bolt before you check headspace. If you don't do this you're wasting your time, and possibly concluding that a dangerous rifle is OK.

Edit: Owen's comment is correct, though. There are some specialty gauges that are built so you don't have to remove extractor/ejector. I assumed the use of standard headspace gauges.

Go to this site:

http://www.m14tfl.com/upload/index.php?

and ask there. Or better yet, search a bit and find the info because it's a question that gets asked a lot.

Tim

 

[lipadj46]

NO GO- This is the max length for a NEW barrel. When installing a new barrel and you have to ream to set headspace you use both GO and NOGO to ensure you don't over ream to far. The ONLY reason to use this gage is when installing a NEW barrel.

FIELD- This gage is used to show when the max allowable headspace has been reached and the weapon should be inspected to confirm what repairs are needed. This is the only gage the military uses to determine if a weapon is safe to fire. "Max allowable chamber dimension".

I don't know the 7.62 Nato Field and No Go gauges I have seen measure to the same length.

 

[Jeremy2171]

NOGO and FIELD gages are different lengths no matter the caliber.....