7.62 NATO/.308 compatability


PDA






Blue1
March 7, 2013, 10:16 PM
Can 7.62 NATO be safely fired from .308 Win chambers? Can .308 Win be safely fired from 7.62 NATO chambers?

Thanks,
Blue1

If you enjoyed reading about "7.62 NATO/.308 compatability" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
303tom
March 7, 2013, 10:27 PM
YES................

HankB
March 7, 2013, 10:33 PM
Generally yes . . . but headspace differences do matter; if you have a 7.62 NATO rifle with headspace on the long side of the 7.62 NATO spec, it may not be such a good idea to shoot .308 Winchester in the rifle.

Here's a discussion of the issue from Fulton Armory:

http://www.fulton-armory.com/faqs/M14-FAQs/308.htm

Trueno
March 7, 2013, 10:34 PM
Commercial chamber pressures generally run a good bit higher than NATO pressures. Keep in mind also that a lot of .308 bullets are in the 180-190 grain range and will beat up a semi-auto.

PSL's, CETME's, G3's...I prefer 147gr 7.62x51 in em.

t

Blue1
March 7, 2013, 11:41 PM
OK, but I'm just wondering if I can use the NATO round in my bolt-action Savage.

Blue1

Blue1
March 7, 2013, 11:49 PM
Ok, this is what I found in a Yahoo questions site:

.308 Win vs. 7.62x51--The Straight Scoop
Before we go much further, lets address the oft-posed question "Are the .308 Winchester and 7.62x51 NATO one and the same?" The simple answer is no. There are differences in chamber specs and maximum pressures. The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62x51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win "Go Gauge" is 1.630" vs. 1.635" for the 7.62x51. The .308's "No-Go" dimension is 1.634" vs. 1.6405" for a 7.62x51 "No Go" gauge. That said, it is normally fine to shoot quality 7.62x51 NATO ammo in a gun chambered for the .308 Winchester (though not all NATO ammo is identical). Clint McKee of Fulton Armory notes: "[N]obody makes 7.62mm (NATO) ammo that isn't to the .308 'headspace' dimension spec. So 7.62mm ammo fits nicely into .308 chambers, as a rule." You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62x51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max..... Reloaders should also note that military ammo often is made with a thicker web. Consequently the case capacity of 7.62x51 brass is usually less than that of commercial .308 brass. You may need to reduce recommended .308 Winchester loads by as much as 2 full grains, if you reload with military 7.62x51 brass, such as Lake City or IMI.

Source(s):

http://www.thegunzone.com/30cal.html

http://www.303british.com/id36.html

http://www.6mmbr.com/308Win.html

http://en.wikipedia.org/wiki/.308_Winche…

http://en.wikipedia.org/wiki/7.62x51mm_N…

Like the 5.56x45MM verses the .223? --- NOpe... Look here for info on that....

http://www.thegunzone.com/556v223.html

http://www.6mmbr.com/223Rem.html

Blue1

USSR
March 8, 2013, 08:26 AM
Sorry Blue1, but you've got it all wrong regarding the pressures. The 7.62x51 pressure spec's of 50,000 psi that you quote were obtained using the copper crusher method and are essentially C.U.P. pressure. The military is not beholden to SAAMI rules, so they can call C.U.P. pressures psi or banana splits if they want, but obtaining the pressure the way they did equates to about 60,000 psi obtained using SAAMI methods. So, there are no problems interchanging the two cartridges aside from perhaps differences in heavier bullets and slower burning powders which may not be compatible to M1/M14 platforms.

Don

madcratebuilder
March 8, 2013, 08:44 AM
The pressure difference between .308 and 7.62 in insignificant. Much confusion from the different measurements, CUP vs PSI. There is not a reliable formula to convert one to the other. Head space and case wall thickness are the major differences.



From a piece FALPhil wrote.

The pressure difference between the two rounds is insignificant, the real problem is commercial ammunition has thinner cases that were not designed to shoot in military chambers BUT we do it all the time anyway and this why you see more case head separations on commercial cases fired in military chambers.

The M118 special long range round is loaded to 52,000 CUP (all other U.S. 7.62mm are 50,000 CUP) which would be equal to the pressure levels of commercial ammunition, this means actually there is no pressure difference between the .308 and 7.62 NATO for the M118 cartridge. No accurate conversion between copper crusher and true pressure exists, but approximations can be made. In all the conversions outlined above, pressures are in thousands of PSI (KPSI). Expect errors of several KPSI, or about 15%, with such formulas. Many factors determine how much the indicated pressure reading from a crusher misses the true pressure, and the error varies among cartridges and even among different loads for one cartridge. The conversions might be accurate enough for many practical purposes.

So, to sum everything up, the pressure difference between the 308 Winchester and the 7.62x51mm NATO is less than 2,000 PSI which is statistically insignificant. The same pressure variation may be
achieved by firing any rifle on a hot day and on a cold day or by changing brands of primers.

Sav .250
March 8, 2013, 08:51 AM
I`d just go with the round it`s designed for. Peace of mind goes a long way.

Reloadron
March 8, 2013, 09:04 AM
Every now and then we like to have a thread on this subject. This thread is a good example. (http://www.thehighroad.org/showthread.php?t=703329)

As has been pointed out the chamber specifications do vary in that a 7.62 NATO has what can be viewed as a slightly larger chamber. This allows a military rifle used under adverse conditions to be more forgiving in chambering a round. This is also apparent as was mentioned in headspace gauge dimensions being different.

While in my experience the actual case outside dimensions have been identical. The military cases do have slightly less volume and have slightly thicker brass in the web at the bases of the case. I wish I had more 7.62 NATO factory loaded ammunition to measure as I was limited to some South African stuff.

The pressures have also been covered in that a .308 Winchester cartridge is measured in PSI (Pounds Square Inch) while the 7.62 NATO pressure is measured in CUP (Copper Units Pressure). There is no simple cross reference between the two nor is there a simple math conversion formula. My understanding here is that there is really very little pressure difference.

This is all on my summer bucket list. I hope to do an in depth study between the two for comparison purposes.

Finally in the link is a picture of a box of .308 Winchester, that same box is also labeled 7.62 NATO as another member pointed out. Unfortunately the box end flap is not clearly visible in the picture. :(

So my understanding is that while a .308 Winchester and 7.62 NATO chamber are not necessarily cut to the same specifications, the cartridges are identical as to outside dimensions. I have fired both in my M1A, AR10 and my Remington .308 bolt gun.

Just My Take
Ron

jmr40
March 8, 2013, 09:25 AM
Short answer, for you use it won't hurt a thing. If you were trying to use commercial 308 ammo in a rifle chambered for 7.62 Nato ammo about the worst thing that would happen is that SOME ammo might not cycle reliably in SOME rifles.

A lot is made of slightly different specs in ammo pressure and slighlty different chamber sizes. Pick any chambering, 243, 30-30, 30-06, 270, any of them, and you will find they are loaded to different chamber pressures depending on the manufacturer. Same with rifles. The tolerences between various rifles in any chambering can be just as great as the differences between typical 308 and 7.62 Nato rifles.

chicharrones
March 8, 2013, 11:23 AM
Just because photos are . . . photos. :evil:

WardenWolf
March 8, 2013, 11:30 AM
The short answer is, a 7.62 NATO round will always work just fine in a .308, but a .308 round may cause problems in a gun designed for 7.62 NATO. The civilian loads are often a bit hotter, and have a wider range of bullet weights that can sometimes cause problems for semi-auto actions.

Double Vision
March 8, 2013, 12:41 PM
Thanks again Reloadron!

Reloadron
March 8, 2013, 04:06 PM
You're welcome Double Vision.

What I would like to find is some Lake City and maybe a few other manufacturers of 7.62 NATO ammunition. This summer once the house bucket list is done I really want to drag myself and some instrumentation out to the range and do some experimenting.

I want to chronograph some loads, especially identical loads in commercial and military brass. I also want to snag some data on pressure curves from different ammunition.

Have to check out some gun shows for assorted 7.62 NATO stuff.

I know what I should see and know it has been done before, just a few things I want to try. :)

Ron

pseudonymity
March 8, 2013, 08:11 PM
Short answer, for you use it won't hurt a thing. If you were trying to use commercial 308 ammo in a rifle chambered for 7.62 Nato ammo about the worst thing that would happen is that SOME ammo might not cycle reliably in SOME rifles.

I am not so sure about that. Take some .308 brass that has been FL resized a few times and put it in a 7.62 chamber that is long enough to close on a SAAMI spec .308 field gauge, and I think you are flirting with a case separation.

.308 brass is designed to safely deform to a maximum length defined by SAAMI. A 7.62 chamber can be longer than that max SAAMI length and still be within NATO spec.

303tom
March 8, 2013, 11:07 PM
The short answer is, a 7.62 NATO round will always work just fine in a .308, but a .308 round may cause problems in a gun designed for 7.62 NATO. The civilian loads are often a bit hotter, and have a wider range of bullet weights that can sometimes cause problems for semi-auto actions.
So you are saying that .308 Winchester may cause problems for my semi-auto huh ?

jonnyc
March 9, 2013, 04:46 PM
"The civilian loads are often a bit hotter"

Nope, sorry, just not true.
As stated above, they are they same round and factory ammo is perfectly interchangeable. Commercial and military chambers are designed and spec'd differently, but the rounds are the same.
Your mother is your father's wife, your aunt's sister, your kid's grandma, etc....same person.

Trueno
March 9, 2013, 08:43 PM
"The civilian loads are often a bit hotter"

Nope, sorry, just not true.
As stated above, they are they same round and factory ammo is perfectly interchangeable. Commercial and military chambers are designed and spec'd differently, but the rounds are the same.
Your mother is your father's wife, your aunt's sister, your kid's grandma, etc....same person.



aaaaaannnnndddddd.........we're off!


I'll start some popcorn!

SaxonPig
March 9, 2013, 09:21 PM
People keep arguing that they are not the same but I have never noted any problems firing one or the either from my rifles no matter what caliber is stamped on the gun. If there is any real difference I can't tell.

Casefull
March 9, 2013, 11:35 PM
I shoot and reload both and use them interchangeably from bolt, semi auto, mil spec, etc. This is a tired, worn out, and ignorant discussion. If you know enough about shooting and reloading then you know the differences would only affect a 1000 yard competitor.

Robert
March 9, 2013, 11:38 PM
Aaaaand we're done here.

If you enjoyed reading about "7.62 NATO/.308 compatability" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!