7.62x51 in a .308

[1 SIG fan]

Is it ok to shoot 7.62x51 in a rifle chambered for .308?

could it cause damage? less accuarcy?

or is it like shooting .223 out of a 5.56 AR?

Thanks.

[sb_pete]

yes, no, and it depends.

Yes it is ok to shoot 7.62NATO out of a gun chambered for .308
No, it will not damage the gun (the reverse is not true - no .308 in a 7.62NATO chamber)
It depends on the ammo and the barrel. Surplus M80 ball will shoot worse than Fed GMM (duh), and 1:10" twist bbls might not like lightweight M80 ball.

.308 has a higher max pressure std than 7.62x51mm so it is ok to shoot 7.62X51mm NATO rounds out of a firearm chambered for .308. The reverse is not a good idea - (SAAMI/CIP max pressure for 7.62NATO is 50,000 PSI, .308 Win is 62,000PSI).

That said, most modern firearms in the class (bolt guns, M1A, AR10, FAL, FNAR, etc) are simply chambered for the higher pressure .308. The issue is in older guns and ESPECIALLY conversions to 7.62x51 from older chamberings like .303, 7.5X55mm Swiss, etc. A notorious problem is the Indian Ishapore Enfields which were chambered for 7.62NATO and should never ever be used to fire .308. The metallurgy is not up to the task of handling the higher pressure

With .223/5.56mm NATO it is the reverse. The military cartridge is loaded to higher pressure than the civilian so loading 5.56mm NATO rounds into .223 chambers is a less than great idea. Also, with .223/5.56, there are other small dimensional differences in the chamber that can affect accuracy (why for instance there are .223, 5.56 NATO, and Wylde chambers (amongst others). With .308 and 7.62NATO, there are also small dimensional differences, but they are less of a concern.

Here is another good response to your question.

hth,
-Pete

[MasterYong]

yes, no, and it depends.

Yes it is ok to shoot 7.62NATO out of a gun chambered for .308
No, it will not damage the gun (the reverse is not true - no .308 in a 7.62NATO chamber)
It depends on the ammo and the barrel. Surplus M80 ball will shoot worse than Fed GMM (duh), and 1:10" twist bbls might not like lightweight M80 ball.

.308 has a higher max pressure std than 7.62x51mm so it is ok to shoot 7.62X51mm NATO rounds out of a firearm chambered for .308. The reverse is not a good idea.

That said, most modern firearms in the class (bolt guns, M1A, AR10, FAL, FNAR, etc) are simply chambered for the higher pressure .308. The issue is in older guns and ESPECIALLY conversions to 7.62x51 from older chamberings like .303, 7.5X55mm Swiss, etc. A notorious problem is the Indian Ishapore Enfields which were chambered for 7.62NATO and should never ever be used to fire .308. The metallurgy is not up to the task of handling the higher pressure

With .223/5.56mm NATO it is the reverse. The military cartridge is loaded to higher pressure than the civilian so loading 5.56mm NATO rounds into .223 chambers is a less than great idea.

+1

It's basically the opposite of the 5.56/.223 issue. (.223 Rem is OK in 5.56 chamber but 5.56 is NOT OK in .223 Rem chamber.)

7.62NATO in a .308 chamber is OK (marked .308 on the rifle).

.308 in a 7.62NATO is most likely NOT OK due to pressure issues. Don't do it.

[MudCamper]

I learned about this difference AFTER I bought my Remington R-25. And although I can shoot 7.62 in my 308 rifle, it's hellaciously inaccurate. While I can shoot 1 inch groups at 100 yards with dollar-per-round 308 ammo, inexpensive 7.62 ammo shoots 6 inch groups. Disappointing.

[MasterYong]

I learned about this difference AFTER I bought my Remington R-25. And although I can shoot 7.62 in my 308 rifle, it's hellaciously inaccurate. While I can shoot 1 inch groups at 100 yards with dollar-per-round 308 ammo, inexpensive 7.62 ammo shoots 6 inch groups. Disappointing.

I think that's because most ammo marked 7.62 NATO (maybe all, I'm not sure) is milsurp which of course isn't going to be as accurate as commercial-grade hunting or target ammo.

I've never got better than 2 MOA out of my 5r with 7.62 milsurp ammo, and rarely get that good of results. I can get 9/16" 5-shot groups at 100 yards using Blank Hills Gold 168gr .308 though, and I'm sure the rifle could do better with a better shooter.

[1 SIG fan]

OK, so in my new savage .308. I CAN shoot the ball surpls 7.62x51 and it won't hurt. BUT, don't expect to zero a scope or have any accuracy.
think i got it. Thanks!

[MasterYong]

OK, so in my new savage .308. I CAN shoot the ball surpls 7.62x51 and it won't hurt. BUT, don't expect to zero a scope or have any accuracy.
think i got it. Thanks!

You could zero a scope. You could have accuracy. Just don't expect better than 4MOA- could be better could be worse depending on the ammo.



For a .308 bolt-gun (if it is indeed a bolt-gun, I can't recall if Savage makes a semi-auto, esp in .308) I would only bother with high-quality match ammo. You can really get it dialed in with hand loads or if you look around online for posts about what others use in your particular make/model or rifle. That's how I found out about the BHG 168gr .308 for my 5r- others had done well with it and it worked for me too.

[buffybuster]

Usually you can shoot 7.62x51 ammo in a .308Win with no safety issues. However, occasionally you will run into odd lots of surplus 7.62Nato ammo that is difficult to chamber in a .308Win rifle (due to headspace spec differences).

[Sailormilan2]

From Fulton's website:
This is a perennial topic, kinda like ".45 vs. 9mm" or "Best Guns & Loads for Deer."

They are not the same.

They are the same.

They are not the same, 'cause the .308 Win was released by Winchester several years before the Army standarized the T64E3 as the 7.62MM. You'll get an endless discussion of pressure specs, endless because SAAMI and the Ordnance Dep't measured pressure in different, unrelateable ways. Howver, the chamber drawings are different.

They are the same, 'cause nobody (and Clint's been looking for many years!) makes 7.62MM ammo that isn't to the .308 "headspace" dimension spec. So 7.62MM ammo fits nicely into .308 chambers, as a rule.

But in some 7.62MM rifles the chambers are long (to the 7.62MM military spec), notably the Navy Garands with 7.62MM barrels. Thus, using commercial ammo in such a rifle is not a good idea; you need stronger brass. Use military ammo or the best commercial only, e.g., Federal Gold Medal Match.

Most of the time it's a distinction without a difference. But if you intend to shoot .308 commercial in a military arm chambered for 7.62MM, first check the headspace with .308 commercial gauges first. You may get a surprise.

Best regards,

Walt Kuleck
Fulton Armory webmaster


--------------------------------------------------------------------------------
Clint, What's the difference between .308 Winchester & 7.62x51mm NATO?

Jerry Kuhnhausen, in his classic Shop Manual (available from Fulton Armory; see the M1 Rifle Parts & Accessories or M14 Rifle Parts and Accessories Pages under Books) has published a somewhat controversial recommendation concerning .308 Winchester and 7.62x51mm NATO ammo, headspace & chambers. I broached the subject with him some months ago. He had his plate full, so we decided to chat on this in the future. When we do I'll report the results of our conversation.

I completely agree with Jerry that if you have a chamber with headspace much in excess of 1.636 (say, 1.638, SAAMI field reject), you must use only U.S. or NATO Mil Spec Ammo (always marked 7.62mm & with a cross enclosed by a circle) since the NATO mil spec calls for a far more "robust" brass case than often found in commercial (read .308 Winchester) cartridges. It is precisely why Lake City brass is so highly sought. Lake City brass is Nato spec and reloadable (most NATO is not reloadable, rather it is Berdan primed). Indeed, cheaper commercial ammo can fail at the 1.638 headspace (e.g., UMC) in an M14/M1 Garand. Many military gas guns (e.g., M14 Rifles & M60 Machine guns) run wildly long headspace by commercial (SAAMI) standards (U.S. Military field reject limit for the M60 & M14 is 1.6455, nearly 16 thousandths beyond commercial (SAAMI) GO, & nearly 8 thousandths beyond commercial (SAAMI) field reject limit!).

I also agree that 1.631-1.632 is a near perfect headspace for an M14/M1A or M1 Garand chambered in .308 Winchester. But I think that it also near perfect for 7.62mm NATO!

I have measured many, many types/manufacturers of commercial and NATO ammo via cartridge "headspace" gauges as well as "in rifle" checks. If anything, I have found various Nato ammo to be in much tighter headspace/chamber compliance than commercial ammo. Indeed, sometimes commercial ammo can not be chambered "by hand" in an M14/M1A with, say, 1.631 headspace (bolt will not close completely by gentle hand manipulation on a stripped bolt, although it will close & function when chambered by the force of the rifle's loading inertia), though I have never seen this with NATO spec ammo. I.e., if anything, NATO ammo seems to hold at the minimum SAAMI cartridge headspace of 1.629-1.630, better than some commercial ammo!

So, why set a very long 1.636 headspace in an M14/M1A or M1 Garand? It probably is the conflict mentioned above. Military headspace gauges say one thing, SAAMI headspace gauges say something else, as do the spec's/compliance covering ammo. In a court of law, who will prevail? I think Kuhnhausen gave all those who do this work a safe way out. However, I believe it not in your, or your rifle's, best interest. Whether you have a NATO chambered barrel (M14/M1 Garand G.I. ".308 Win."/7.62mm NATO barrels all have NATO chambers), or a .308 Winchester chamber, keep the headspace within SAAMI limits (1.630 GO, 1.634 NO GO, 1.638 FIELD REJECT). This subject is a bit confusing, and for me difficult to explain in a one way conversation!

Clint McKee

http://www.fulton-armory.com/

From the American Rifleman:

The AMERICAN RIFLEMAN, February, 2008, p. 20

"Unlike using 5.56x45 mm NATO ammuniton in a .223 Rem.-chambered guns, which the Sportings Arms and Ammunitions Manufacturor's Institute lists in its "Unsafe Arms And Ammunition Combinations," there is no such blanket prohibition in using .308 Win factory ammuntion in 7.62x51 mm rifles, or vice versa, but caution is required. The external cartridge dimensions of the .308 Win. and the 7.62x51 mm NATO are nearly identical, although the 7.62x51 mm barrels have a 0.013" longer chamber specifications, so there could be case head sperations issues with the thinner commercial .308 Win. cases. Also, military 7.62x51 mm loads can be encountered that exceed SAAMI's .308 Win. maximum pressure of 62,000 p.s.i. Of course, it's always best to use ammunition for which the barrel was designed."
__________________

[MR.R]

whould u shoot 308 or 762 in a m1a?

[MasterYong]

whould u shoot 308 or 762 in a m1a?

I think it may depend on the M1A. Consult the manufacturer (I'm not sure if all Springfield's will or not, but my Springfield M1A Scout will do both).

[popeye4]

whould u shoot 308 or 762 in a m1a?

Now you bring in yet another variable in the equation. The M14 gas system is (as is the M1) sensitive to the powder burn rate of the ammo used. The M14 requires moderate speed powder (4895 is the standard that was used in its design) to be used to prevent damage to the gas system. Slower powder may have lower chamber pressure, but it has a higher port pressure at the gas system. Commercial .308 Win ammo does not necessarily use the appropriate powder (none of the Remington commercial does). 7.62 x 51 milspec ammo does use the appropriate powder. Some of the match ammo (such as Black Hills) PROBABLY uses the correct powder, but I'd check with the manufacturer before I risked damaging an expensive rifle.

If you handload, you can use the right burn rate powder.

[MasterYong]

Now you bring in yet another variable in the equation. The M14 gas system is (as is the M1) sensitive to the powder burn rate of the ammo used. The M14 requires moderate speed powder (4895 is the standard that was used in its design) to be used to prevent damage to the gas system. Slower powder may have lower chamber pressure, but it has a higher port pressure at the gas system. Commercial .308 Win ammo does not necessarily use the appropriate powder (none of the Remington commercial does). 7.62 x 51 milspec ammo does use the appropriate powder. Some of the match ammo (such as Black Hills) PROBABLY uses the correct powder, but I'd check with the manufacturer before I risked damaging an expensive rifle.

If you handload, you can use the right burn rate powder.

I'm not trying to be argumentative, but I emailed Springfield before I bought my M1A and they stated that the rifle would fire commercial .308 or milsurp 7.62NATO with no ill effects. They trying to sell me parts?

[buffybuster]

The M14/M1A uses a different gas system than the M1 Garand.

The M1 Garand gas system had to be used with a specific powder burn rate and bullet weight range, to not damage the operating rod. Gas flow in this system is not cut off. Powder and bullets outside of the design parameters could overstress the system (usually resulting in a bent op-rod).

The M14/M1A uses an updated gas system that is self-limiting and is not as critical of powder burn rate and bullet weight. In this self-limiting system, when the gas cylinder achieves adequate gas pressure/volume, the gas piston moves to cut off gas flow. This is a relatively forgiving system BUT it was NOT DESIGNED to be used with Light Magnum or other bolt action only ammunitions loaded with specific powders to extend the pressure curve.

[MR.R]

te reason i asked is i shot some 308 in my m1a and it didnt work, the majority of the ammo did not eject. then tryed some remington,and black hills no problems at all