Field testing for headspace problems

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Gergify

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Alright I've asked similar questions about this but this one is a bit different. I'll be shooting my Polytech M1a Friday. I have not purchased a headspace gauge, because I'm clueless on how to use one. However after reading through the discussions about Polytech's with soft bolts, I'm a bit paranoid about shooting mine now :p. I don't want anything exploding on me...

Its suggested that I check the headspace it after shooting. However since I don't have a gauge nor the knowledge to use it, and bringing it to the nearest gun smith will be a costly (and time consuming) adventure, especially doing each time I shoot.

I was wondering if there is a way to tell if the head space is going bad simply by examining the bolt itself and/or the spent casings (aka, without the aid of a gauge). I heard that if the casing is starting to split near the neck and/or there is backed out primer; that could be sign of excessive headspace. However will this method give me accurate results constantly?

If not, then I'll have to take it to the gunsmith, I'd rather keep my hand.
 
I can't believe anyone would recommend you check headspace every time you shoot the rifle. Maybe after 500 rds or so to see if it's increasing, then make a decision as to if you're dealing with a rapid wear issue.

A single headspace gauge (the "FIELD" size) is only around $27 or so. If your bolt won't close on this, and you are shooting military surplus ammo (not reloaded milsurp brass), you are probably OK. Opinions differ on this, but that's how the military used the gauge. If the bolt closes, you have to either rebarrel or find a bolt with a closer fit.

To properly use the gauge, you need to disassemble the bolt. There's a tool that makes this easy, or you can just struggle without the tool... :) Be careful you don't get parts in your face!

That way the ejector and extractor aren't interfering with the "feel" of the bolt closing.

Leave the op-rod detached, too. Then insert the gauge in the chamber and close the bolt on it. If the bolt lug doesn't drop in the notch, you're good. If it does drop in, you have excessive headspace. Don't force the bolt...you're just trying to see how it fits with the steel gauge.

For commercial (thinner) brass and reloads, you should be using a "NO GO" gauge, which is shorter, and the bolt should not close on that one.

As to your question of examining fired brass, excessive headspace sometimes creates a bright ring at the top of the web, around 1/4" or so from the head, from the thinning of the brass. A sharpened, bent paper clip can be used as a probe to feel for this groove inside the brass. If you have the ring or the groove, you're on the path to case head separation.

This is just one person's opinion, and like a lot of things, there is no warranty expressed or implied.

As I have no experience with "soft" receivers, you'll have to look to another resource to answer the question "Is it safe to shoot?" even if it doesn't have excessive headspace.
 
It's a two minute job for a smith to check it. Do they even charge for that? Mine doesn't.
 
You do not have to keep checking it forever. Get a field gauge check it before you shoot it and then after the first time you shoot it. Then just check it periodically to make sure you are good. If the bolt is soft you will see it pretty quickly. If it has already been shot and the headspace checks out chances are you are fine. Just remember Springfield Armory Inc. had this same problem back in the 90's before they went to a forged bolt so it does not make the polys or norincos garbage.
 
It has nothing to do with cracked necks.

Backed out primers, maybe.

The bent paper clip dmazur outlined in Post #2 will indicate a stretch ring inside the case after firing.

If there isn't one you can feel, you don't have a problem.

rc
 
I'm in a similar boat to you Gergify. I've got an unfired Polytech M14S. I have the extractor & ejector out of my bolt. I have a NO GO 308 Win. gauge. I'll test it tonight & report back.

I've also read that the Polytech's were chambered for 7.62x51 NATO and I should be using a NATO head space gauge, and it'll just swallow my 308 gauge. My receiver is stamped for 308 WIN.

I hope to shoot mine Saturday.

I'm confused. :confused:
 
Yes you should use a 7.62 Nato field gauge as the M14 clones usually have a military type chamber that is a little looser than a commercial .308 chamber. Dimensionally a .308W shell and 7.62x51 shell are the same beast (well outer dimensions at least). Your Norinco may swallow a .308 No Go gauge and still be perfectly fine. Try though and let us know.

You can get the Nato field gauges from Numrich for pretty cheap though.
 
I'm in a similar boat to you Gergify. I've got an unfired Polytech M14S. I have the extractor & ejector out of my bolt. I have a NO GO 308 Win. gauge. I'll test it tonight & report back.
Click to expand...

The No GO gage is only used when installing a new barrel. I'll tell you right now that your chamber will swallow it whole.

The 7.62NATO Field Reject is the one you need.
 
Well I'm shooting it today. I hate to take a risk on this, but I'm sure its been fired before. I haven't ordered a headspace gauge yet, but I will sometime before next week.

Should I just bag the idea of shooting it today, or just be cautious when doing so?
 
What makes you think you have a problem?

I know you talked about weak steel in the bolt, and that this gun has been fired before, but is there any other things that have you worried about the rifle?

Most of the ranges I go to have a knowledgeable person there somewhere, usually installing and bore sighting scopes. Ask one of the them to check the rifle. It is in their best interest for you to be shooting a sound weapon on their range.


Good Luck,
 
The only thing worse than a technical note is a technical note with errors -

Other gages may be produced at dimensions between the minimum and maximum dimensions to allow other considerations to be tested such as remaining barrel life for a particular purpose (i.e “overseas deployment” or “field reject”).
Click to expand...
- Italics added to show the error

This was taken from the Armalite link, which IMO was otherwise excellent.

In decreasing size order, headspace gauges are FIELD, NOGO, and GO. Some use the difference between NOGO and FIELD as a measure of remaining life before rebarreling is necessary, and some just flat-out state that anything larger than NOGO is unsafe. I have found good arguments on both sides of this practice, with the key seeming to be whether military spec ammo is being used or not. As most are aware, this is thicker brass that has not been fired.

The GO/NOGO gauges were used during finish reaming of a new barrel, to make sure you had a chamber that was "near" NOGO. As the Armalite note describes, this provides an acceptable clearance for ammo variations and should prevent "failures to close". The FIELD gauges were used by military armorers "in the field" to check rifles in for repair to see if the headspace had increased to a dangerous point. Headspace OK, make other repairs and reissue. Not OK? Toss it in the pile to be rebarreled.

30Cal has it right. If you just want to do the military armorer's safety check, get a FIELD gauge for 7.62 Nato.
 
Heck, yes shoot it. A single fired case will tell you if you have any problems. If nothing is wrong, it won't hurt to check every hundredth case -- or every case, which you will do anyway, if you reload.
 
As suspected, the bolt closed on my 308 win NO GO gauge (1.634). Guess I'll be needing the NATA field gauge in the future.

Now I can't get the bolt reassembled :banghead:
 
Now I can't get the bolt reassembled
Click to expand...

Chamber a spent 30-06 case and compress your bolt springs against it as you push the extractor back in. By far the quickest and easiest way.
 
headspace

There is also a quick way and thats to glue a thin piece of card stock on the head of the cartridge and close the bolt,if you cant close the bolt the headspace is ok.
the steel is ok in the noricos its the heat treatment that may not have been done there is a company that heat treats the guns.I have a welded M1 garand that had to be anneld to machine and I called the arsenal and was told its fine it just may wear faster.It is a carbine in 308.and I shoot anything in it.it was checked by one of the best in saugust mass.:rolleyes::uhoh:
 
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