Is it ok to shoot .308 in a rifle chambered for 7.62x51mm?

[desidog]

OP, FYI my M1A Loaded has ".308" printed on the NM barrel, not "7.62"

 

[Redneck with a 40]

My dad's FNAR is stamped with 7.62x51mm on the barrel, we e-mailed FN to ask if commercial .308 was safe to fire. They responded that all commercial .308 is safe to fire in the FNAR. This may or may not apply to other rifles, but its safe in the FNAR.

 

[TexasRifleman]

The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62x51 max is 50,000 psi.

One is measured in psi, one in cup (copper units of pressure).

They are NOT the same thing but you can correlate between the 2 systems. (see articles below)

There is a typo in an army field manual from decades ago that shows the "50,000 psi" number for NATO ammo. That is incorrect but people keep quoting it like it's from the Bible or something.

However, the European agency that tests ammo for NATO (CIP) has published documents showing NATO 7.62x51 to have a max pressure of 60,200 psi.

So, 60,000 vs 60,200 psi appears in documents quite often.

That's the same pressure folks.....

If you want to read into it, here are a few places:

http://www.shootingsoftware.com/ftp/psicuparticle2.pdf

http://www.chuckhawks.com/pressure_measurement.htm

What you should be concerned with is headspace, not chamber pressures.

 

[W L Johnson]

When in doubt, check with whoever made your gun (if possible) and see what they say.
If you still have doubt, box it up and ship it to me.

 

[wishin]

Is it ok to shoot .308 in a rifle chambered for 7.62x51mm?

Buttrap, the OP was rifle related.

 

[SaxonPig]

I have shot some commercial 308 in both my FAL and my HK91 and never noticed a lick of difference between it and military ammo. I suspect any differences are very minor and within manufacturing tolerances.

PS: I can't discern any difference in report or recoil between commercial 308 and most military 7.62 but I have shot some military ammo (maybe Indian or Pakistani, not sure) that definitely felt and sounded hotter than the rest.

 

[W.E.G.]

Its up to the owner of the gun to figure out whether "its OK" or not.

I've never heard of .308 causing any sort of catastrophic failure in 7.62 rifles. While it may be true that .308 has a higher SAAMI-spec rating than 7.62 NATO, that certainly does not mean all commecial .308 is loaded to maximum SAAMI spec.

I have heard of commercial .308 (Winchester white box IIRC) not reliably extracting from some CETME and/or HK-type (delayed-blowback) rifles. Some reports indicated the delayed-blowback guns literally ripped the case heads. Its not clear to me whether the reports were head-separations, or the extractor ripping through the rim before the case would let go of the chamber. If indeed the .308 had higher pressure, it would be my opinion that the "brass not letting go" is a likely cause. Moreover, if you ever got your hands on Pakistani ammo designed especially for the fluted 7.62 chamber, you will notice a waxy coating on the ammo. This is another let-go-of-the-chamber feature you won't find in Remington .308 ammo bought at Dick's Sporting Goods.

Similarly, I have heard of 7.62 ammo not reliably extracting from DPMS LR-308 type rifles. Whether this is a function of too little gas pressure from the foreign-made 7.62 milsurp ammo, or is a function of external dimensions of the ammo, I do not know.

I measured various milsurp 7.62 ammo. One batch of Malaysian linked machine-gun ammo significantly exceeded the conventional .308 spec of 1.630" from the base of the cartridge to the datum-line on the shoulder. The only .308 I had on hand at the time of my measurements was a box of Federal Gold Medal .308. The Gold Medal measured within about 0.002" of the measurements I was getting for several of the various milsurp 7.62. I wrote a "report" of sorts on these measurements. You can read my report at http://www.falfiles.com/forums/showthread.php?postid=2160133#post2160133

One might speculate that third-world machine-gun ammo tends to be of greater "headspace" dimension (longer from base to shoulder datum-line) as the guns used by those countries are more worn-out than brand-new American guns. So much for a "standard" NATO spec.

Here's a quick summary of the "report."

 

[madcratebuilder]

One is measured in psi, one in cup (copper units of pressure).

They are NOT the same thing but you can correlate between the 2 systems. (see articles below)

There is a typo in an army field manual from decades ago that shows the "50,000 psi" number for NATO ammo. That is incorrect but people keep quoting it like it's from the Bible or something.

However, the European agency that tests ammo for NATO (CIP) has published documents showing NATO 7.62x51 to have a max pressure of 60,200 psi.

So, 60,000 vs 60,200 psi appears in documents quite often.

That's the same pressure folks.....

If you want to read into it, here are a few places:

http://www.shootingsoftware.com/ftp/psicuparticle2.pdf

http://www.chuckhawks.com/pressure_measurement.htm

What you should be concerned with is headspace, not chamber pressures.
__________________

Correct answer, it's head space you need to know.

 

[Ben Shepherd]

Ok, I'll eat a bit of crow right here, out in public. There are sources on both sides of the isle that are supposed to be reliable, however, SAMMI currently lists 308 and 7.62X51 as 62,000 and 60,200 respectively. Since they are the "policy makers" as it were, fine, I stand corrected by folks wiser than myself.

I will note that in my personal experience that commercial 308 has almost always shown higher velocities over my chrono than surplus 7.62X51, which would in most(not all) cases correlate with higher operating pressures.

 

[powermad]

Good grief..
Does the search feature not work anymore?
How about a sticky with the 1,500,000 posts of will .308 work in a 7.62x51 gun?

 

[TexasRifleman]

I will note that in my personal experience that commercial 308 has almost always shown higher velocities over my chrono than surplus 7.62X51, which would in most(not all) cases correlate with higher operating pressures.

That's probably the case. Surplus NATO 7.62 ball seems to me to be loaded well below the max.

The MAX pressures are pretty much the same, but I have no doubt that off the shelf loads will have higher pressure in .308.

 

[USSR]

Quote:
The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62x51 max is 50,000 psi.

One is measured in psi, one in cup (copper units of pressure).

They are NOT the same thing but you can correlate between the 2 systems. (see articles below)

There is a typo in an army field manual from decades ago that shows the "50,000 psi" number for NATO ammo. That is incorrect but people keep quoting it like it's from the Bible or something.

However, the European agency that tests ammo for NATO (CIP) has published documents showing NATO 7.62x51 to have a max pressure of 60,200 psi.

So, 60,000 vs 60,200 psi appears in documents quite often.

That's the same pressure folks.....

Thanks, TexasRifleman, I was just getting ready to post the very same thing. Why do we constantly have to explain this?

Don

 

[Ben Shepherd]

For the same reason that others have to explain that it's OK to carry a 1911 cocked and locked, and others have to constantly explain the differences between a magazine and a clip(Says the hunter-ed instructor who sees 50 plus students a month, mostly with 10/22s fed by "clips":banghead.

There's a lot of misinformation out there on this subject, and I for one am glad that somebody posted the info so I could learn something new today.(Thanks TR)

 

[richardluther]

As a test, I took some .308 and some South African Ball and alternated them in a mag in my Portuguese G3.

Could NOT tell the difference. FWIW I've blown hundreds of .308 in my G3 without problem. However, the difference in damage to the casing is real with the .308 being dented much more than my milsurp.

I'd love to know if over time (say 2000 rounds of .308 later) will I be damaging my rifle by not shooting exclusively milsurp?

Great posts.

 

[TexasRifleman]

However, the difference in damage to the casing is real with the .308 being dented much more than my milsurp.

Keep in mind NATO brass is thicker than commercial .308. It may be just as simple as that; thin brass dents easier.

 

[jonnyc]

Hurt a G3 with .308 ammo...I think not, not in 100,000 rounds.

 

[mlr1m]

I choose to remain on the cautious side. Op-rods for M1-A's are very expensive. I stay with good quality military ammo or my own reloads.

Michael

 

[lobo9er]

ArmaLite’s® larger AR-10 series rifles are all chambered with 7.62 NATO
chambers. .308 Winchester (SAAMI standard) ammunition functions perfectly in the 7.62 NATO chambers.

we e-mailed FN to ask if commercial .308 was safe to fire. They responded that all commercial .308 is safe to fire in the FNAR.

manufactures say its ok i am willing to bet FN and Armalite have a handle on things

Good grief..
Does the search feature not work anymore?

The search engine is not that great on this site.

 

[AKElroy]

I for one am glad that somebody posted the info so I could learn something new today.

Thank you. If we all used the search function on every topic as satisfactorily addressing every issue, this site would have been closed to new posts in 2003. Yes, topics are repeated. So are comments. But new participants arrive everyday, and I learn something here nearly everytime I log in. I have yet to get irritated over someone asking the same question; I am sure I have done it often.

God bless those individuals that have all available firearms knowledge. I have yet to arrive.

 

[lobo9er]

One is measured in psi, one in cup (copper units of pressure).

They are NOT the same thing but you can correlate between the 2 systems. (see articles below)

There is a typo in an army field manual from decades ago that shows the "50,000 psi" number for NATO ammo. That is incorrect but people keep quoting it like it's from the Bible or something.

However, the European agency that tests ammo for NATO (CIP) has published documents showing NATO 7.62x51 to have a max pressure of 60,200 psi.

So, 60,000 vs 60,200 psi appears in documents quite often.

That's the same pressure folks.....

USSR, TEXASRIFLEMAN, I'm on their side.

 

[TexasRifleman]

I choose to remain on the cautious side. Op-rods for M1-A's are very expensive. I stay with good quality military ammo or my own reloads.

That's an entirely different thing. That has as much to do with burn RATES of the powder as the chamber pressures. Some powder burn rates are much faster, giving you a spike in recoil, smacking the op rod, where some powder types ramp up the recoil in a more progressive manner because the powder is a bit slower. Gas operated rifles tend to not like fast burning powders.

Tons on this topic, interesting stuff:

http://www.reloadbench.com/burn.html

In this chart it lists common powders from fastest to slowest burn rate. Notice that BL-C(2) is nicely in the middle. That's a common milspec type of powder.

Certainly everyone has to decide for themselves, but chamber pressures are not all that's involved here, that's for sure.

 

[Casefull]

Years ago I picked up some linked 7.62 mg ammo and shot it in my hk91 and it was noticeable hotter than the 308 rounds we had. My brother shot two rounds in his remington pump and it broke the bolt. In that instance the military ammo was stouter than the 308.

 

[mlr1m]

I choose to remain on the cautious side. Op-rods for M1-A's are very expensive. I stay with good quality military ammo or my own reloads.

That's an entirely different thing. That has as much to do with burn RATES of the powder as the chamber pressures. Some powder burn rates are much faster, giving you a spike in recoil, smacking the op rod, where some powder types ramp up the recoil in a more progressive manner because the powder is a bit slower. Gas operated rifles tend to not like fast burning powders.

This is exactly why I mentioned it. The OP mentioned a SOCOM was on his list of possible rifles.

Michael

 

[dmazur]

Some powder burn rates are much faster, giving you a spike in recoil, smacking the op rod, where some powder types ramp up the recoil in a more progressive manner because the powder is a bit slower. Gas operated rifles tend to not like fast burning powders.

Actually, it's a pressure curve thing. Slower powders can have a longer curve, and it's the tail of the curve where you measure port pressure. If it's too high at that instant in time, the op-rod gets bent.

So, there is an "acceptable powder burn rate" region. Not too slow, and not too fast.

 

[nathan]

SInce we are talking of these again , will the Ishapore 2 A 1 handle the .308 ammo okey? LEt say, the Brown Bear 145 gr FMJ commonly sold today ?