M305 Headspaced at .1638

walleyed99

walleyed99

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It has been measured at .1638, so this would make it at the field reject size. So therefore not safe to shoot .308 ammo? or just not reloads? or what? any suggestions to tighten up the chamber, would a new bolt(usgi,lrb) do it? Wanting to eventually have a new barrel,and bolt installed but for the time being will just adding a new bolt tighten it up enough? advice....

Thank for the help guys
cheers
w99
 
well commercial .308 is not safe to fire.

If you get once fired brass, or fire form yourself, you can FL size it to spec with your chamber.

Bolt sometimes helps, with a new barrel and bolt it can be corrected. real/after market barrels are genraly cut to better standards in the first place.
 
Well, if you're exactly 1.638, quite honestly I would still be comfortable firing it if you monitor it for further increase. If it will simply close freely on a FIELD gauge (1.638") and the exact headspace is unknown, it is definitely unsafe to fire and your remedy is a new bolt, which unfortunately costs about as much as an M305.

From Forster, I'm sure you've googled all this up already but can't hurt to share, so if you're snug on a field, I wouldn't panic yet.

FIELD (1.638"): Corresponds to the longest safe headspace. If a rifle closes on a FIELD gage, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gages are slightly shorter than the SAAMI maximum in order to give a small safety margin.
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In my experience, and what I have told clients and folks at clinics, 1.640" and I'd start keeping an eye on commercial .308 brass for signs of pressure. Previous to 2009's arrivals, the average norc/poly came in between 1.640 to 1.644.
Starting with '09 we saw quite constantly, the rifles measuring 1.636" to 1.638". This average has leaned towards 1.638" on most rifles I've measured since 09. We're talking about 200 plus 09"s to 2013's .
In a rack grade m14, 1.638" ain't that bad and is still within National Match specs for 7.62 nato.
I shot nothing but federal powershok 150gr thru every former client's rifles measuring 1.638" and everything is still attached.
Just use good ammo for .308 stuff and watch for pressure signs by collecting all your brass and inspecting once and a while.
 
walleyed99 said:
It has been measured at .1638, so this would make it at the field reject size. So therefore not safe to shoot .308 ammo? or just not reloads? or what? any suggestions to tighten up the chamber, would a new bolt(usgi,lrb) do it? Wanting to eventually have a new barrel,and bolt installed but for the time being will just adding a new bolt tighten it up enough? advice....

Thank for the help guys
cheers
w99
Click to expand...

Forgot the new barrel part. In a perfect world, I would change the barrel and bolt at the same time if you're going ahead with it. It's just a lot less hassle to do it once, especially if going with a chrome lined Criterion or USGI, as for all intents and purposes they can't be reamed deeper to adjust headspace and you're working with what you can lap off the bolt and lugs alone. It is possible to ream a chrome lined barrel, but you need a carbide reamer and it's generally not recommended.

If you're choosing a non-chromed barrel that is short chambered like a Krieger then you have one more variable on your side, in that you can use a pull through reamer (though setting the barrel shoulder still requires a lathe) to cut a chamber to perfect headspace. So in this case if you plan on buying non-lined and reaming, you're good to go ahead and lap in an American bolt as final headspace will be determined by the reamer, not the bolt's lapping. It would only need to be lapped into good lug contact which you would have already done with the Norc barrel.
 
For what ever reason Norinco used the caliber designation of 308 Winchester and not 7.62x51 Nato, I'll never know. Maybe to appeal the the North American market, perhaps.

I say this because there is a difference in the tech spec for 7.62x51 NATO military rifles vs 308 win civilian rifles.

For rifles chambered in 7.62 NATO, here are the headspace limits (in inches):

GO: 1.6355"
NO-GO: 1.6405"
FIELD: 1.6455"

For .308 Winchester chambers:

GO: 1.630"
NO-GO: 1.634"
FIELD: 1.638"

So you can see the difference, So .1638 is tighter than a Nato No go gauge.

Since it was mentioned, the issues with commercial 308 win is the thickness of the base of the cartridge, Nato cartridges are thicker and are designed to work with generous chamber dia.
So keep an eye out for deformities etc, like we all do when shooting any firearm. If you want tighter head spacing, I suggest to read the stickies, lots of good information there.

Pete
 
1.639 here, 4th reloads don't show any alarming signs in or outside of the brass shooting 2750fps and 150g bullets, but I'm not going to push 5. This is loading 308win brass, not 7.62x51

I'll keep shooting this 1.5 inch grouping barrel for another 2-3000 rounds and then spend some money on something else more expensive and hope I get the same accuracy lol
 
Cool, Thanks for the input fellas! Kinda what I was thinking but not %100 sure. There is so much conflicting reports on the web that one cannot be sure. On CGN, I am hearing guys shooting .308 in guns head-spacing bigger than .1638, then you read another report saying it's not safe. Thanks for restoring my confidence, I will just keep a close eye on my brass and not worry about the headspace. If it gets any larger, then I will look at doing a barrel, and bolt replacement.
 
Some brass is better than others, I was very unhappy with my new win 30-06 brass, The base of the cartridge case around the primer pocket was hollow like a shot gun shell.



Rocket Surgery said:
1.639 here, 4th reloads don't show any alarming signs in or outside of the brass shooting 2750fps and 150g bullets, but I'm not going to push 5. This is loading 308win brass, not 7.62x51

I'll keep shooting this 1.5 inch grouping barrel for another 2-3000 rounds and then spend some money on something else more expensive and hope I get the same accuracy lol
Click to expand...
 
Cool, Thanks for the input fellas! Kinda what I was thinking but not %100 sure. There is so much conflicting reports on the web that one cannot be sure. On CGN, I am hearing guys shooting .308 in guns head-spacing bigger than .1638, then you read another report saying it's not safe. Thanks for restoring my confidence, I will just keep a close eye on my brass and not worry about the head-space. If it gets any larger, then I will look at doing a barrel, and bolt replacement.
 
Once you know what you're doing with these rifles, you'll be able to tell who doesn't quite easily. I'm not trying to be an internet elitist douche or anything, but I've probably got the equivalent of a DeVry diploma in M1A's now.

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Well, I am in the just learning stages, but trying to learn as much as I can! Unfortunately, i will not be able to take part in Hungry / Tactical Teacher M14 clinic in Dundurn due to scheduling conflicts that I just cannot get out of!DAMN! so its down to reading, reading and more reading. The only problem is for everyone that knows what they are talking about, the next 2 or 3 don't have a clue! Once you figure out who to listen to, its all good!!

Cheers
Rob
 
Beauty of the M14 is there really isn't much to them. Extremely simple firearms mechanically as far as semis go. Tuning one to perfection takes some mild witchcraft but the standard mechanic work is likely the simplest I've encountered in semis. Thankfully lots of parts available too.
 
Looks like I got luck after all! I managed to get the 16th off and will now be able to partake in Hungrys Dundurn clinic :rockOn:, so will hopefully learn a ton! I can unfortunately only make day one of the 2 day course but I am really really looking forward to it! Now, I wonder if I can find another m14 and get it to me before next Tuesday :)
 
Bring some fired brass for measuring for the 16 July clinic and we'll ensure yer #### don't fall off. Remember that this is the innernet (sic) and information is not always the most reliable. :D

Cheers,
Barney
 
Hi Walleyed, make sure you turn off your gas system when firing for brass to measure so that the action stays locked throughout the expansion, you'll get the most accurate measurement that way :cheers:
 
Rocket Surgery said:
1.639 here, 4th reloads don't show any alarming signs in or outside of the brass shooting 2750fps and 150g bullets, but I'm not going to push 5. This is loading 308win brass, not 7.62x51

I'll keep shooting this 1.5 inch grouping barrel for another 2-3000 rounds and then spend some money on something else more expensive and hope I get the same accuracy lol
Click to expand...

Rocket if you could, take a once fired case and a 4th reload(5 firings) section them and post the pictures if you could just curious of what 1.638 looks like after 5 firings. When I was still hand-loading(press is in a tote box for years now) I used to section different brass in rounds I was pushing very hot(My 7mmRemMag 66grs4831,CCI250 175SBT@3050fps for one) to actually see the incipient separation as it occurred just forward of the head. This is where brass is robbed from during full length resizing to feed that trimmer:cool:.
 
"...the field reject size..." No such thing. It's just a 'Field' guage. Headspace guages do not measure anything. They only tell you if the rifle's tolerances are within spec. When a rifle is headspaced, nothing is set to a specific number. Only the guages are used. If the bolt closes on a Go, but not on a No-Go, the job is done. The Field is only used, not used at all by military weapons techs, if the bolt closes on the No-Go.
"...308win brass, not 7.62x51..." They are the same thing. Despite what you see on-line. Millions of rounds of both have been fired and reloaded interchangeably long before there was such a thing as the Internet.
 
Are you saving that brass and reloading it? Or just shooting it the once? With the numbers you have given, simply firing a new 308 cartridge shouldn't cause a problem. Its the strain on the case from resizing and then stretching it back out again that will take its toll on the brass. Mine is around that number and shoots factory 308 just fine.
 
762NATO brass while dimensionally the same 99.7% outside to .308Winchester, has a reduced internal capacity from thicker walls. Just take any once fired NATO case and a commercial .308Win, weight them empty on your loading scale and then filled to the mouth with water. By the differential you will see that the NATO round will hold around 2-3 grains less IIRC.

Years back when I extensively handloaded, if I got my hands on IvI NATO brass or Imperial .308Win brass, the internal capacity was lesser than Fed, Rem, Win etc etc. Apparently from by own deductions, as I have never seen it in print, when IvI loaded their commercial .308Win for the canadian market, they must have running the same brass they were loading for DND in 762NATO.
What this translated to in chamber pressure and resulting velocities with the same powder/primer charge worked up to max loads in a specific rifle,.. say in Remington cases,... and then applied to an Imperial case, I can't tell you. Now I wish I had done a velocity comparison over the chrony with my pet load of the day for sale, 165 Hornady Spire point over 46.5grs WW748/CCI250. A superbly accurate load in every rifle I fired it through, and even took a mediocre Browning Lever .308 from 2.5-3MOA down to 1.25". Nothing else could touch this load in this fussy rifle.


Wish I has some old loads lying around to try in the M-14. Maybe I'll have to set up the bench again! I know this powder burn rate/bullet combo may be a little hard on the M-14 op rod, I would have liked to see if it tightened up groups appreciably in my stock NorincoField M-14s.
 
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