Thanis

I posted a few questions about 5.56x45mm NATO vs .223 Rem.

5.56x45mm vs .223 Remington

I gathered in that thread that there are advantages to going with a 5.56x45mm NATO firearm as it will safely fire both 5.56x45mm NATO and .223 Rem safely. The problem, unlike .38 Spl vs .357 Mag, where the more powerful .357 Mag will not fit into a .38 Spl firearm, the 5.56x45mm NATO will fit and fire in a .223 Rem chambered firearm. The common wisdom, there is a safety issue using the more powerful 5.56x45mm NATO in a .223 Rem chambered firearm.

Now I have a similiar question concerning the 7.62x51mm NATO vs .308 Win. I've been told they are safely interchangeable. Then I read that they are not, and unlike a .223 in a 5.56x45mm firearm, a .308 Win is not safe to fire in a 7.62x51mm firearm, in addition, a 7.62x51mm should not be fired in a .308 Win firearm.

Toughts?

In addition, something about a summary from the link confused me. Can anyone clarify this for me:

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

"The worst case scenario for shooters of 7.62 NATO rifles is as follows: Using a commercially made, maximum pressure cartridge with long headspace, fired from a weak action (ex. converted 93/95 Mausers)."

What?

"The weaker action is a possible final piece of the 308 vs 7.62 NATO puzzle."

What?

__________________
NRA Member
S&W 642 (no-lock) with .38 Spl +P 135 GR Gold GDHP
Glock G31 & G33 with .357 Sig 125 GR. SXT Winchester Ranger

NativH

I'm interested in the answer also. I have an Armalite AR10 and typically use Hornady TAP 308 when I mean business and Winchester 308 FMJ for practice. I did get 10 boxes of Winchester 7.62 NATO FMJ and figure my Armalite will handle it fine. My biggest concern is how the action will operate with the slightly higher pressure since I haven't had a chance to try the NATO rounds yet.

__________________
SE Texas Patriot Guard Rider, NRA Patron, TSRA Life Member (and according to the wife , just a regular old a**hole)

Thanis

I'm a real novice at this, I'm thinking here is the problem.

Military round out of civilian firearm, firearm is the weak link. (but this may be what I'm wrong about)
The weak link when firing a 7.62x51mm NATO out of a .308 Win chambered firearm is the firearm might not be able to take the additional pressure of the 7.62x51mm NATO. The 7.62x51mm NATO pressure is greater then the .308 Win chambered firearm rating.

Civilian round out of a military firearm, civilian round is the weak link. (think I get this one)
The weak link when firing a .308 Win out of the 7.62x51mm NATO chambered firearm has nothing to do with the pressure on the firearm, but the pressure on the brass of the .308 Win round. The 7.62x51mm NATO chambered firearm has more play in the chamber then the .308 Win chambered firearm.

Is that it?

--or--

I also get the idea, that the commercially made, maximum pressure cartridge of the .308 Win might have a few more grains of powder (becase there is less brass / more space in the .308). This then confuses me, because it sounds like the concern is that the military firearm can't handel the pressure of the max pressure civilian round. So if the .308 Win chambered firearm can take this additional pressure, why cant it take the 7.62x51mm NATO's pressure?

If this is correct, then it would mean then:

To safely interchange 5.56x45mm NATO & .223 Rem. you need the military 5.56x45mm NATO chambered firearm.

To safely interchange 7.62x51mm NATO & .308 Win you need the civilian .308 Win chambered firearm.

Is that it?

__________________
NRA Member
S&W 642 (no-lock) with .38 Spl +P 135 GR Gold GDHP
Glock G31 & G33 with .357 Sig 125 GR. SXT Winchester Ranger

Fisherman

I thought that 7.62x51 was the same thing as .308 Win. Same brass and all. Is that wrong?

I learn something every day. I sure would like to get an M1A. They'd probably cycle anything you'd feed it.

__________________
I ain't what I otta be, I ain't what I wanta be, I ain't what I could be,

But thank God, I ain't what I used to be,
And, Praise God, I ain't what I'm gonna be!

II Cor 3:18

gumaro

Read this...



"308 Win vs. 7.62x51--The Straight Scoop
Before we go much further, we want to 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. For more information on this interesting topic, read the following articles: Gun Zone's 30 Caliber FAQ; Cruffler.com Technical Trivia, June 2001; and last, but not least, Steve Redgwell's .308 vs 7.62x51 Analysis, which really provides a definitive explanation. 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."

found at
.308 Winchester Cartridge Guide

NativH

gumaro,

Great info. Sounds like I'm good to go with shooting NATO out of my 308 AR-10. I would have thought that the NATO had more pressure than the 308 but I'm wrong again. Now I wonder how the NATO rounds will cycle my AR-10's bolt. Guess I'll find out next time I'm at the range.

__________________
SE Texas Patriot Guard Rider, NRA Patron, TSRA Life Member (and according to the wife , just a regular old a**hole)

gumaro

I believe it will cycle okay, I have a couple of FAL rifles, they have a gas regulator so you can adjust it to cycle different ammo. Also when buying commercial ammo you might also consider the softer primers used in the .308 and .223, as opposed to the NATO or mil-surplus ammo. Some people have had slam fires, because the FAL, AR 15, and AKs have a floating firring pin. I also got a Mauser Yugo M48 action that I will make into a .308. The Mauser action is strong and should handle both, but I plan on shooting reloads only.

Thanis

Well interesting.

To safely interchange 7.62x51mm NATO & .308 Win you need the civilian .308 Win chambered firearm, because the civilian round may have more max pressure than the military.

---contrast---

To safely interchange 5.56x45mm NATO & .223 Rem. you need the military 5.56x45mm NATO chambered firearm, because the military round may have more max pressure than the civilian.

__________________
NRA Member
S&W 642 (no-lock) with .38 Spl +P 135 GR Gold GDHP
Glock G31 & G33 with .357 Sig 125 GR. SXT Winchester Ranger

Fisherman

Gumaro - Thanks for the info!

__________________
I ain't what I otta be, I ain't what I wanta be, I ain't what I could be,

But thank God, I ain't what I used to be,
And, Praise God, I ain't what I'm gonna be!

II Cor 3:18

dukalmighty

All I ever shot out of my AR10 is 7.62x51 surplus ammo,probably over 2000 rounds to date

__________________
I like Poetry,Long Walks On The Beach,And Poking Dead Things With A Stick