7.62x51 in a .308...kaboom???

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patriot53

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Ok, did not happen to me...
...however this months "Rifle Shooter" magazine, has a featured article on the RUGER SR762 AR10 "type" rifle.

This "writer", Patrick Sweeny, says "Ruger told me that they chambered the gun in .308WIN..."
...then he, (Sweeny, NOT Ruger...) says ; "so for the SAME reason it is not safe to fire 5.56NATO in a rifle chambered for .223...
...you should stick to .308 in the Ruger SR762...for the SAME reason, in case of HOT military rounds..."
???
I think he's (Sweeny) has got that ALL WRONG...backwards?
I've always understood that for the .308 ONLY and 7.62 ONLY chambered Rifles it was just the OPPOSITE of the relationship between 5.56 & .223.

That if a rifle was "chambered" ONLY for 7.62x51...
...then it could be hazerdous to FIRE .308WIN in such rifle, because it's the .308 rounds that are typically loaded far more "HOT" than 7.62x51?

Correct me if I'm wrong...I've been "wrong", before, once...lol:D
However, I think Mr. Sweeny needs to check his "facts" BEFORE writing articles?
 
Yep that's it and it it hits you in the toe it will come out the top of your head!

:rolleyes:
 
There are some minor differences in SAAMI dimensions for both 308 Winchester and the NATO 7.62X51MM cartridges. However, we only have one set of dies to reload both - right? Another thing, both cartridges do have the same pressure maximums. Ok relatively the same to be more exact. The 308 is commonly rated to 62,000 psi and the NATO round to 50,000 CUP. Although no specific conversion from psi to CUP, it is interpreted to be within +-1,500 psi of each other. This notion that the 308 is loaded hotter just isn't so.
 
Been reloading for the past thirty-five years, numerous 7.62X51 & .308 Win firearms, all using the same load recipe in mixed lots of brass. Never had a single issue, failure, or other problem. Thousands of rounds.
One thing to keep in mind: gun publications must constantly come up with something to keep their readers; if they did not, most readers would go away.
 
The ruger is stamped 308/7.62x51 on the barrel. Mine fed everything without a single problem.
 
The .308 has thinner walls than the military nato rounds. Due to this in loose tolerance military rifles they can over expand and then rupture
 
Read the saami list of incompatible rounds. 5.56 NATO and .223 is one of the incompatible combinations. 308 WIN and 7.62x51 is not. Also Armalite has on their website verified their 7.62x51 AR10's are fully compatible with any 308 win or 7.62x51 ammo loaded within saami specs. There have been some instances of foreign countries ammo having problems but that was more lack of QC than incompatibility.
 
It's all about headspace.
.308 Commercial rounds are designed for rifles headspaced to 1.630"-1.634" chamber.
7.62X51 is headspaced to 1.635" min to 1.640" maximum chamber.
Excessive case stretch occurs when shooting commercial .308 ammunition in a nominally or long chambered 7.62X51 which can lead to catastrophic case failure, especially when using the hotter "light Magnum" type factory hunting cartridges.
Catastrophic case failures occur at the case shoulder, not the case head, and can cause chamber failure and or detonation of the receiver area.

For the opposite reason, the longer case dimensioned and thicker case walled 7.62X51 should not be fired in tight commercial .308 chambers.
Doing so can dramatically increase the pressure spike as the cartridge detonates which can cause extreme failure of the weapon including receiver detonation in weak or poorly constructed actions.
The pressure spike can far exceed the 65,000 psi threshold of commercial .308

Another potential issue is failure of the longer, thicker 7.62X51 failing to fully chamber in the shorter commercial .308 chamber leading to the very real possibility of an out of battery detonation or worse, an out of battery slam fire.
This is especially true of semi automatic firearms.

Heed Pat Sweeny's advice.

Reloading for the 7.62X51 is a whole 'nuther discussion.
Do it wrong and you'll be lucky to get two reloads before the case seperates.
 
jhtrue said:
The .308 has thinner walls than the military nato rounds. Due to this in loose tolerance military rifles they can over expand and then rupture
Click to expand...
...which is why you may not want to fire .308 in a 7.62x51 ONLY military rifle, if you were really concerned about that, which I am not...and hence, Mr. Sweeney had it all backwards...
 
Onmilo said:
It's all about headspace.
.308 Commercial rounds are designed for rifles headspaced to 1.630"-1.634" chamber.
7.62X51 is headspaced to 1.635" min to 1.640" maximum chamber.
Excessive case stretch occurs when shooting commercial .308 ammunition in a nominally or long chambered 7.62X51 which can lead to catastrophic case failure, especially when using the hotter "light Magnum" type factory hunting cartridges.
Catastrophic case failures occur at the case shoulder, not the case head, and can cause chamber failure and or detonation of the receiver area.

For the opposite reason, the longer case dimensioned and thicker case walled 7.62X51 should not be fired in tight commercial .308 chambers.
Doing so can dramatically increase the pressure spike as the cartridge detonates which can cause extreme failure of the weapon including receiver detonation in weak or poorly constructed actions.
The pressure spike can far exceed the 65,000 psi threshold of commercial .308

Another potential issue is failure of the longer, thicker 7.62X51 failing to fully chamber in the shorter commercial .308 chamber leading to the very real possibility of an out of battery detonation or worse, an out of battery slam fire.
This is especially true of semi automatic firearms.

Heed Pat Sweeny's advice.

Reloading for the 7.62X51 is a whole 'nuther discussion.
Do it wrong and you'll be lucky to get two reloads before the case seperates.
Click to expand...
Nah...actually Ruger says non of that matters...think they would be worried about liability?
I think so.

Quote : (design of the SR762) : "The bolt assembly is configured similarly to a standard AR, though enlarged to accommodate the 7.62x51 mm NATO cartridge. All of the components are chrome-plated for added lubricity and, therefore, smoother cycling."
Mr. Sweeny's "advice", is all wet.

Also, I DO also have a Ruger Gunsite Scout .308 bolt action....found an interesting post from Ruger, on another forum :

"Here's the email I just received from Ruger.......................

Dear Evan,


Thank you for using the Ruger On-Line Customer Support Request Form.

This e-mail is in response to your question or comment of 01/24/2012
Request No: 123277

Comment / question:

Can I shoot 7.62x51 NATO ammunition in my Ruger Gunsite Scout Rifle?

Thank You,
Evan

Response:
7.62 x 51 NATO can be fired in any and all M77’s and Hawkeyes, including the Scout Rifle chambered in .308 Win.

Note; Military surplus ammunition can vary greatly in its quality and consistency.

Thank you for your interest in Ruger Firearms.

If you need further information, please visit our website at www.ruger.com or contact us at:

Revolvers, shotguns, rifles, 10/22 Charger Pistol: (603) 865-2442
Pistols: (928) 778-6555
Serial Number History Information: (603) 865-2424

Please note: This e-mail is sent from a notification-only address that cannot accept incoming e-mail. Please do not reply to this message.

Sincerely,
Ruger Firearms[/b]

AND;

Re: Ruger tells me not to use 7.62 NATO in GSR *** UPDATE ***
« Reply #19 on: January 30, 2012, 08:29:09 PM »
Quote from: Wapiti on January 30, 2012, 01:01:02 PM
I would like to hear the results of placing chamber gauges in Ruger Scout Rifle:

1. 7.62 X 51 NATO
2. .308 Winchester
(One at a time, of course, lets not get smart! )

Does anyone have both a RSR and the chamber gauges?

Photos, please!
(drool)

Dave

Yes, I have a complete set of headspace gauges, and no, checking the headspace on the RGSR is so low on my list of priorities I'll probably not bother. Ruger chambers to SAAMI dimensions, i.e., .308 Winchester. 7.62x51 cartridges have the same dimensions (including base-to-shoulder-datum) as .308 Win, so the 7.62x51 cartridges work fine in .308 chambers.

For more details, review the treatise on the subject in either The M1 Garand Complete Assembly Guide or The M14 Complete Assembly Guide .

Regards,

Walt"
« Last Edit: March 28, 2013, 04:43:42 PM by wjkuleck »
 
Last edited:
Willie Sutton said:
Where does all this *nonsense* originate?
Click to expand...
Of course, in this case:

Sweeny and "Rifle Shooter" will be R.C.C (Rumor Control Central) for a great many first time readers.

Imagine all the: "I once read..." that will be spoken in the future off this one article only.
 
G.barnes said:
The ruger is stamped 308/7.62x51 on the barrel. Mine fed everything without a single problem.
Click to expand...
Oh...yes, in fact it is.
So I guess that settles it?
Ruger is saying by that "stamping", that it safely fires both.
 
When will it end???

If an occasional 7.62 gun (Navy Garand for example) will close on a .308 Field gauge, don't shoot .308. Otherwise threat them the same. Anything commercial and recent is going to be just fine--even for reloading.

Mike
 
"The 308 is commonly rated to 62,000 psi and the NATO round to 50,000 CUP. Although no specific conversion from psi to CUP, it is interpreted to be within +-1,500 psi of each other."

You don't have to convert or interpret. Before the industry went to piezoelectric transducers, the specs were .308 52,000 crusher psi (now called CUP) versus 7.62 50,500. A meaningless distinction, there can be more difference than that round to round of the same load.

"This notion that the 308 is loaded hotter just isn't so.

True.


I would go by the recommendations at
http://www.fulton-armory.com/\faqs\M14-FAQs\308.htm
particularly noting the part that all 7.62 cartridges inspected were within .308 headspace control length.

It is the military chambers that are "roomy" to insure reliable operation of a hot, dirty automatic weapon. Kulek and McKee recommend knowing your chamber dimensions and if you have a sloppy one, stick to stout military brass.
 
I have absolutely no scientific information about it, however, I have shot some 7.62x51 through a Howa 1500 target in .308 win. It didn't chamber all that great. It seemed to be a good bit tight. Otherwise it had a pleasant lift after firing and shot well for military ammo.

I don't think a modern rifle would fail shooting the NATO version of .308w unless there's a flaw with the ammo or the rifle.
 
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