7.62x51 vs .308 - AR15.COM

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Posted: 1/14/2006 12:27:32 PM EDT

Now I know this question has probably come up many times before but I still need to ask:

My friend has a ruger m77 chambered in .308 (says so on the rifle). Would it be safe to fire 7.62x51 surplus ammo (south african) out of this rifle? I recognize that usually these designations are used interchangably, but that is usually in reference to military rifles with 7.62x51 chambers.
Thanks

Posted: 1/14/2006 12:31:10 PM EDT

[#1]

I believe commercial 308 chambers, have higher toleranes, versus 7.62 NATO chambered weapons....AFAIK.

Someone else will chime in

Posted: 1/14/2006 12:48:20 PM EDT

[#2]

I would feel very safe shooting 7.62 NATO ammo in a Ruger chambered in .308 Win.

I might not feel as good about firing .308 Win ammo in a gun designed for 7.62 NATO ammo. I believe .308 specs allow that ammo to be loaded to higher pressures than 7.62 ammo.

Posted: 1/14/2006 2:41:19 PM EDT

[#3]

Chamber pressures have nothing to do with 7.62 versus .308 or vice versa. The 7.62 chamber is simply built to allow a hair more slop in it to allow for a dirty environment in combat. Nothing more, nothing less.

Shoot mil-surp out of your Weatherby, shoot commercial out of your G3, it won't hurt either one.

Posted: 1/14/2006 2:50:48 PM EDT

[#4]

Quoted:
Chamber pressures have nothing to do with 7.62 versus .308 or vice versa. The 7.62 chamber is simply built to allow a hair more slop in it to allow for a dirty environment in combat. Nothing more, nothing less.

Shoot mil-surp out of your Weatherby, shoot commercial out of your G3, it won't hurt either one.

Damn straight!

Posted: 1/14/2006 3:53:43 PM EDT

[#5]

Quoted:
Chamber pressures have nothing to do with 7.62 versus .308 or vice versa. The 7.62 chamber is simply built to allow a hair more slop in it to allow for a dirty environment in combat. Nothing more, nothing less.

Shoot mil-surp out of your Weatherby, shoot commercial out of your G3, it won't hurt either one.

I was simply pointing out a difference between the two when I said comercial 308 Win can be loaded to higher pressure. Maybe I wasn't clear in why might not want to shoot comercial 308 ammo in a gun designed to 7.62 NATO specs. Like you pointed out the 7.62 can have a looser chamber and that is no problem if your using NATO spec ammo, that has a case that is built to be stronger than SOME comercial brass. Take a LC 7.62 case and weigh it and cut it in half and compare to a Remington 308 case for example and you will see. In most military chambers you will have no problem with comercial ammo, but if your chamber is really loose you are more likely to have a case head seperation using comercial ammo.

Everyone has to make up their own mind what they want to do, so shoot comercial in a 7.62 gun if you want. It will probably work just fine, but then again it might not.

Posted: 1/14/2006 4:47:04 PM EDT

[#6]

the pressures are different.

7.62 has less pressure then 308 due to its thickness of brass.

it is safe to shoot 7.62 in a 308 gun.

it is NOT safe to shoot 223 in a 5.56 gun.

People will tell you it is safe because they are not behind the gun and don't pull the trigger for you.

Posted: 1/14/2006 4:55:03 PM EDT

[#7]

Quoted:

it is NOT safe to shoot 223 in a 5.56 gun.

i think you got that backward.

Posted: 1/14/2006 5:07:05 PM EDT

[#8]

Quoted:
Chamber pressures have nothing to do with 7.62 versus .308 or vice versa. The 7.62 chamber is simply built to allow a hair more slop in it to allow for a dirty environment in combat. Nothing more, nothing less.

Shoot mil-surp out of your Weatherby, shoot commercial out of your G3, it won't hurt either one.

I always thought shooting commercial out of a G3 was a no-no. Being the case was thinner or something. I may be wrong though.

Posted: 1/14/2006 5:09:31 PM EDT

[#9]

Quoted:
Quoted:

it is NOT safe to shoot 223 in a 5.56 gun.

i think you got that backward.

Yup. 5.56 chamber is good to go with .223 and 5.56.

Posted: 1/14/2006 6:23:08 PM EDT

[#10]

I think years ago on AOL gun board there was a guy named Kyrieellis or such that would have a fit over this thread. I don't believe there is a nickles worth of difference in the 2. That said, don't trust an old spanish mauser chambered in .308.

Posted: 1/14/2006 7:49:18 PM EDT

[#11]

The max SAAMI loads for .308 Winchester exceeds the pressure limits of 7.62 NATO, however, these max loads aren't common, and are usually marked "For use in bolt-action rifles ONLY." An example is Hornady's "Light Magnum" loads.

Normal .308 Winchester ammo is loaded to lower pressures consistant with safe operation in 7.62 NATO rifles, as this is a very common application for this ammo.

Yes, the headspace and throat dimensions are generally a bit longer in 7.62 NATO rifles, to allow for extended operation in semi- or full-auto. This is a non-issue here.

The situation is the reverse of 5.56 vs. .223, where the military load is of higher pressure than the commercial load.

-Troy

Posted: 1/14/2006 7:58:22 PM EDT

[#12]

like bobcole said, it's the head space, not the pressure. I have my FAL set at 1.632

Posted: 1/14/2006 8:05:13 PM EDT

[#13]

Quoted:
The max SAAMI loads for .308 Winchester exceeds the pressure limits of 7.62 NATO, however, these max loads aren't common, and are usually marked "For use in bolt-action rifles ONLY." An example is Hornady's "Light Magnum" loads.

Normal .308 Winchester ammo is loaded to lower pressures consistant with safe operation in 7.62 NATO rifles, as this is a very common application for this ammo.

Yes, the headspace and throat dimensions are generally a bit longer in 7.62 NATO rifles, to allow for extended operation in semi- or full-auto. This is a non-issue here.

The situation is the reverse of 5.56 vs. .223, where the military load is of higher pressure than the commercial load.

-Troy

Could you put hot .308 loads in a semi 7.62 gun with some type of adjustable gas block to reduce gas pressures for the cycling?
I personally would be pretty confident the 7.62 chamber itself would handle the hot loads, but would worry that the extra gas pressure would really bang the shit out of the action when cycling it.

Posted: 1/14/2006 8:06:13 PM EDT

[#14]

Quoted:
The max SAAMI loads for .308 Winchester exceeds the pressure limits of 7.62 NATO, however, these max loads aren't common, and are usually marked "For use in bolt-action rifles ONLY." An example is Hornady's "Light Magnum" loads.

Normal .308 Winchester ammo is loaded to lower pressures consistant with safe operation in 7.62 NATO rifles, as this is a very common application for this ammo.

Yes, the headspace and throat dimensions are generally a bit longer in 7.62 NATO rifles, to allow for extended operation in semi- or full-auto. This is a non-issue here.

The situation is the reverse of 5.56 vs. .223, where the military load is of higher pressure than the commercial load.

-Troy

If anyone has an idea what he's talking about when it comes to ammo, listen to this guy.

Posted: 1/14/2006 8:12:50 PM EDT

[#15]

Quoted:
Could you put hot .308 loads in a semi 7.62 gun with some type of adjustable gas block to reduce gas pressures for the cycling?like a FAL
I personally would be pretty confident the 7.62 chamber itself would handle the hot loads, but would worry that the extra gas pressure would really bang the shit out of the action when cycling it.it's more wear, but not much, I also have a buffer for my FAL

Posted: 1/14/2006 8:14:16 PM EDT

[#16]

Quoted:
Quoted:
Could you put hot .308 loads in a semi 7.62 gun with some type of adjustable gas block to reduce gas pressures for the cycling?like a FAL
I personally would be pretty confident the 7.62 chamber itself would handle the hot loads, but would worry that the extra gas pressure would really bang the shit out of the action when cycling it.it's more wear, but not much, I also have a buffer for my FAL

Exactly like a FAL.
You read my mind.

So can you just turn down the adjuster and run the New Hotness through her, or is there other problems associated with using the New Hotness in FAL's that require you to stick with the Old n Busted loads?

If anything would be a selling point for the FAL (For me) it would be the fact I could use any 7.62/.308 load on the planet in the gun by just adjusting the gas valve.

Posted: 1/14/2006 8:35:15 PM EDT

[#17]

I dont think you will have any problem shooting the South African 7.62 in the Ruger Model 77 . I shoot commercial .308 in my FAL Imbel R-1 and have had no problems. Commercial .308 is loaded hotter than the South African Military 7.62.

Posted: 1/14/2006 8:43:37 PM EDT

[#18]

Quoted:
Quoted:
Chamber pressures have nothing to do with 7.62 versus .308 or vice versa. The 7.62 chamber is simply built to allow a hair more slop in it to allow for a dirty environment in combat. Nothing more, nothing less.

Shoot mil-surp out of your Weatherby, shoot commercial out of your G3, it won't hurt either one.

I always thought shooting commercial out of a G3 was a no-no. Being the case was thinner or something. I may be wrong though.

I spilt a commercial case in one, belive it was Rem. ammo and the was surprised how thin the case was. One thing is for sure your day at the range is over if you don't have a broken case extractor handy.

Posted: 1/15/2006 9:57:03 AM EDT

[#19]

Quoted:

it is safe to shoot 7.62 in a 308 gun.

it is NOT safe to shoot 223 in a 5.56 gun.

Wholly incorrect. I, along with probably millions of others, have done this very thing. I don't know where you got your info, but I sure wouldn't use them as a source ever again.

Posted: 1/15/2006 9:58:20 AM EDT

[#20]

Quoted:

I always thought shooting commercial out of a G3 was a no-no. Being the case was thinner or something. I may be wrong though.

I have done this many times. No problems what so ever.

Posted: 1/15/2006 9:59:40 AM EDT

[#21]

Quoted:
like bobcole said, it's the head space, not the pressure.

Pity you couldn't have set my ex-wife's head space!!!!!

Posted: 1/15/2006 10:15:00 AM EDT

[#22]

Quoted:
Quoted:
The max SAAMI loads for .308 Winchester exceeds the pressure limits of 7.62 NATO, however, these max loads aren't common, and are usually marked "For use in bolt-action rifles ONLY." An example is Hornady's "Light Magnum" loads.

Normal .308 Winchester ammo is loaded to lower pressures consistant with safe operation in 7.62 NATO rifles, as this is a very common application for this ammo.

Yes, the headspace and throat dimensions are generally a bit longer in 7.62 NATO rifles, to allow for extended operation in semi- or full-auto. This is a non-issue here.

The situation is the reverse of 5.56 vs. .223, where the military load is of higher pressure than the commercial load.

-Troy

Could you put hot .308 loads in a semi 7.62 gun with some type of adjustable gas block to reduce gas pressures for the cycling?
I personally would be pretty confident the 7.62 chamber itself would handle the hot loads, but would worry that the extra gas pressure would really bang the shit out of the action when cycling it.

You can buy the same thing for Garands, you replace the threaded cylinder plug and use different replaceable "ports" to allow it to allow safely with the proper pressure. For that matter you can shut off the gas on a M1A and go single shot.

Posted: 1/15/2006 2:07:55 PM EDT

[#23]

Quoted:
Quoted:
Quoted:
Could you put hot .308 loads in a semi 7.62 gun with some type of adjustable gas block to reduce gas pressures for the cycling?like a FAL
I personally would be pretty confident the 7.62 chamber itself would handle the hot loads, but would worry that the extra gas pressure would really bang the shit out of the action when cycling it.it's more wear, but not much, I also have a buffer for my FAL

Exactly like a FAL.
You read my mind.

So can you just turn down the adjuster and run the New Hotness through her, or is there other problems associated with using the New Hotness in FAL's that require you to stick with the Old n Busted loads?you have to make sure the head space is ok, use 1.632 in a FAL and it's perfect for 308, and 7.62

If anything would be a selling point for the FAL (For me) it would be the fact I could use any 7.62/.308 load on the planet in the gun by just adjusting the gas valve.then go buy one

Posted: 1/15/2006 10:07:58 PM EDT

[#24]

Quoted:
Could you put hot .308 loads in a semi 7.62 gun with some type of adjustable gas block to reduce gas pressures for the cycling?
I personally would be pretty confident the 7.62 chamber itself would handle the hot loads, but would worry that the extra gas pressure would really bang the shit out of the action when cycling it.

NO! Full-power .308 rounds are very near 7.62 NATO proof load pressures, and the actions on guns like the FAL, CETME/G3/HK91, and M14/M1A are NOT designed for this much pressure. It isn't about the gas volume causing cycling problems; it's about the gun going kBoom!

Thus the reason that the vast majority of .308 loads are downloaded to safe 7.62 NATO pressures. Even some older .308 guns won't stand up to these loads, so be careful.

-Troy

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