M14S Headspace Check From Fired Brass

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M14CheatOtoole

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I have recently purchased an M14S, reciever is marked 2007. The dealer I bought it from assured me it was perfectly safe to shoot commercial .308. This was confirmed by the importer as well when I spoke to them to order some accessories.
I have joined this forum and am very impressed at the depth of knowledge and the positive comments regarding the M14S, something not found on some of the sites based to the south.
I have seen that some members have generously offered to determine headspace by inspecting expended brass. My question is: would these members consider posting their techniques? I am a DIY kind of guy with a good set of calipers and would like to monitor the headspace regularly.

I really like the M14S and this site.
 
You take several fired cases and measure them with a precion mic
guage.This will tell you how much the case expands in the chamber.
Most Norcs are about .009 over the spec.I know some people if you sent
them 5 cases would measure them for you.Hungry used to do this.
Or you could just get your own 50 to 60 dollars.This way if you reload
you can resize just enough to chamber easily.The brass will last much
longer but remember it may not chamber in other 308 rifles.
 
Being an engineer/mechanic type I already have all the measurement tools, just need to know what I am looking for. Looking on Wikipedia they show the case length in the drawing from base to end as 55.46mm. However they also list case length as 51.2mm. Which measurement are we going off of?
 
Overall case length is not the measurement you are looking for. This is not necessarily an indication of headspace. The tool saskshooter mentionned references off the shoulder. If the shoulder has moved foreward too much when fireformed, then there can be an issue of excess headspace.
 
Buy a set of headspace guages. A No-Go will do. Mind you, you won't have to monitor the headspace.
"...something not found on some of the sites based to the south..." That's because they can only get early Polytech's and Norinco's since Clinton banned their importation. The early models supposedly had headspace and part quality issues. Mind you, it may have to do with the rifles not being made Stateside.
 
sunray said:
"...something not found on some of the sites based to the south..." That's because they can only get early Polytech's and Norinco's since Clinton banned their importation. The early models supposedly had headspace and part quality issues. Mind you, it may have to do with the rifles not being made Stateside.
Click to expand...

I think most of it had to do with the fact that the Norcs and Polys were priced far cheaper than Fulton Armoury's competing '14s. A lot of the warnings about the early Chinese '14s quality can be traced back to Clint McKee and Fulton.
 
I would guess that to get any useful information out of fired brass you would have to shut off the gas system. After all the brass isn't finished expanding when it gets yanked out of the chamber, so if you want to precisely measure something, you might as well precisely measure something that's actually representative!

I have read a few places that there's no point measuring fired brass from M14s...I don't believe this, I do think you'd better shut off the gas system first.
 
sunray said:
Buy a set of headspace guages. A No-Go will do. Mind you, you won't have to monitor the headspace.
"...something not found on some of the sites based to the south..." That's because they can only get early Polytech's and Norinco's since Clinton banned their importation. The early models supposedly had headspace and part quality issues. Mind you, it may have to do with the rifles not being made Stateside.
Click to expand...

That is not the issue here. The issue is how does one measure head spacing using fired brass. I have access to gauges but am interested in furthering my knowledge.
 
You want the RCBS Precision Micrometer in .308 Win.............they are $59.99 at WSS.....................

88302.jpg
Micrometer reading of the cartridge chamber dimension and bullet seating depth.

They are a handy tool to have on hand...........

SKBY.
 
Skullboy - Thanks for the info. That's where I need to start. Should kill two birds with one stone as I am curious about headspace and may eventually get into reloading also.
 
THe RCBS gauge looks like this:

rcbs_go_gauge_b.jpg


rcbs_go_gauge_a.jpg


For absolute headspace I don't like them much as I have several and they all measure this .308 go gauge differently (this one in particular is bad....3 thou short. They are pretty useful for relative headspace measurments though , but only once you index them as a reference point using a headspace gauge you know to have been ground accurately. In the example illustrated in the above photos, either the RCBS gauge measures 3 thou short or the headspace GO gauge is 3 thou short...I have many gauges; several from the same manufacturer and several others from other manufacturers. In this case the headspaces gauges all measure the same (although I have one gauge NO-GO gauge from a well known manufacturer that is way way way to long...but I digress) so it is the RCBS gauge I believe is wrong. This was confirmed by purchasing two more and having one of them measure correctly and the other one measuring 1 thou long. What is up with that?? Someone should ask RCBS how they calibrate these things....:(

So....if you are going to use the RCBS tool, get yourself a good GO gauge to use as a reference (1.630 in .308win) and then you can use the RCBS gauge to measure your spent brass as an indication of headspace. I would follow misanthropist's advice and shut off the gas system; I have seen some ammo that burns to quickly or is overpressured somewhat and results in the phenomenon he describes...brass stretch due to the case not being fully relaxed before the extractor yanks it rearward. The result is deceptively long headspace readings.

Anyway...good luck with your project!

Brobee
 
In case nobody else has offered (didn't read the whole thread), I'd be happy to mic your fired brass for you, as I have one of those RCBS thingies. Just drop me a PM if you are interested.
 
Ok, tell me if I'm out to lunch. This is something I tried and I'm not sure how accurate it is.

I loaded a primed case with a couple grains of Bullseye, stuffed a paper wad in the case mouth, chambered it and fired it. The primer backed out as expected because there wasn't enough pressure to stretch the case to fill the chamber. So then I measured the the amount that the primer was out of the primer pocket with the depth gauge end of an electronic caliper. Iirc, it measured about .007". Isn't this showing how much headspace the rifle (Norc M305) has?
 
762shooter said:
Ok, tell me if I'm out to lunch. This is something I tried and I'm not sure how accurate it is.

I loaded a primed case with a couple grains of Bullseye, stuffed a paper wad in the case mouth, chambered it and fired it. The primer backed out as expected because there wasn't enough pressure to stretch the case to fill the chamber. So then I measured the the amount that the primer was out of the primer pocket with the depth gauge end of an electronic caliper. Iirc, it measured about .007". Isn't this showing how much headspace the rifle (Norc M305) has?
Click to expand...

Somehow I don't think this is an accurate way of measuring................if you think you haven't stretched the case enough to fill the chamber, how is that a true reading???

SKBY.
 
This test would show that there is about a .007" difference between this particular cartridge case, and the headspace of this rifle. Could vary from case to case. You don't know where the case would fall within the manufacturing tolerance range for cartridge cases, so the starting point is not really known. Gauges can establish specific tolerance ranges, the RCBS tool can determine actual measurements.
 
tiriaq said:
This test would show that there is about a .007" difference between this particular cartridge case, and the headspace of this rifle. Could vary from case to case. You don't know where the case would fall within the manufacturing tolerance range for cartridge cases, so the starting point is not really known. Gauges can establish specific tolerance ranges, the RCBS tool can determine actual measurements.
Click to expand...

Good point. It was a full length sized case, though. Would that make any difference to your comments?
 
Skullboy said:
Somehow I don't think this is an accurate way of measuring................if you think you haven't stretched the case enough to fill the chamber, how is that a true reading???

SKBY.
Click to expand...

A very light load like this wouldn't expand the case at all, that's the point of the test. There is enough pressure to push out the primer to take up the headspace.
 
762shooter said:
Good point. It was a full length sized case, though. Would that make any difference to your comments?
Click to expand...

Relative to that particular sizing die, you are observing about .007" difference between the casing and the breeching dimensions of the rifle. Another consideration is what would happen with a brand new case. IF the headspace is generous, first firing could be hard on the case. Fl sizing will restore the case dimensions, but doesn't address whether or not there could be an incipient separation.
It would be interesting to try your experiment with a brand new case, and see if there is any difference, if the primer protrusion is in the same range.
Using a set of headspace gauges to check the rifle, or the RCBS tool to measure brass will give more specific information.
 
Brobee said:
THe RCBS gauge looks like this:

rcbs_go_gauge_b.jpg


rcbs_go_gauge_a.jpg


For absolute headspace I don't like them much as I have several and they all measure this .308 go gauge differently (this one in particular is bad....3 thou short. They are pretty useful for relative headspace measurments though , but only once you index them as a reference point using a headspace gauge you know to have been ground accurately. In the example illustrated in the above photos, either the RCBS gauge measures 3 thou short or the headspace GO gauge is 3 thou short...I have many gauges; several from the same manufacturer and several others from other manufacturers. In this case the headspaces gauges all measure the same (although I have one gauge NO-GO gauge from a well known manufacturer that is way way way to long...but I digress) so it is the RCBS gauge I believe is wrong. This was confirmed by purchasing two more and having one of them measure correctly and the other one measuring 1 thou long. What is up with that?? Someone should ask RCBS how they calibrate these things....:(

So....if you are going to use the RCBS tool, get yourself a good GO gauge to use as a reference (1.630 in .308win) and then you can use the RCBS gauge to measure your spent brass as an indication of headspace. I would follow misanthropist's advice and shut off the gas system; I have seen some ammo that burns to quickly or is overpressured somewhat and results in the phenomenon he describes...brass stretch due to the case not being fully relaxed before the extractor yanks it rearward. The result is deceptively long headspace readings.

Anyway...good luck with your project!

Brobee
Click to expand...

How's about the stoney point comparator! It's way more accurate than the RCBS unit - uses a digital caliper and measures off the shoulder datum line.

Glen Zediker has it all in his loading book. He even has a section on the M14 because he loaded service rifle for years.

Hope this helps,

Carl
 
If a guy could still get the stoney point doo-hicky I'd be all over it...unfortunately I've had one on order from wholesale sports for over a year now. Anyone else out there carry them?
 
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