.308 vs. 7.62

[Waveman]

I read that  .308 and  7.62 ammunition are no necessarily interchangeable.  Can I safely shoot .308 in a DPMS 7.62 x 51 chambered upper?

[dirigoboy]

Yes, you can shoot .308 in the 7.62  You should only shoot .308 in the .308 rifle however.  Look on the bottom side of your barrel.  If it is stamped 7.62 you can shoot either.  If it is stamped .308, shoot only .308 in it.

[Madhouse]

This is the same condition as the 5.56x45mm versus .223 Rem.  The NATO rounds (5.56x45 and 7.62x51mm) are a little higher pressured.  Anything rated for 5.56 or 7.62 can shoot the .223 and .308 counterparts, but not vice versa.

[98Z5V]

The .308 vs. 7.62 is the opposite of the .223 vs. 5.56 stuff - .308 is rated up to a higher pressure than the 7.62 counterpart round...  I think the last numbers I found were something like 48k psi in the 7.62 cartridges vs. a 62k psi max in the .308 Win cartridge.

The people that need to be cautious of this are the guys that shoot older military surplus rifles.  A high pressure .308 Win round can have some bad effects in an old milsurp rifle.

The modern semiauto rifles don't suffer so much from it - .308 or 7.62 chamber in the modern guns with modern manufacturing - typically not a problem.

Anytime this is brought up on the 'net messageboards, it turns into a big fat debate.  I'll find some links I've got on the info and post it into this response.

[imschur]

The .308 vs. 7.62 is the opposite of the .223 vs. 5.56 stuff - .308 is rated up to a higher pressure than the 7.62 counterpart round...  I think the last numbers I found were something like 48k psi in the 7.62 cartridges vs. a 62k psi max in the .308 Win cartridge.

The people that need to be cautious of this are the guys that shoot older military surplus rifles.  A high pressure .308 Win round can have some bad effects in an old milsurp rifle.

The modern semiauto rifles don't suffer so much from it - .308 or 7.62 chamber in the modern guns with modern manufacturing - typically not a problem.

Anytime this is brought up on the 'net messageboards, it turns into a big fat debate.  I'll find some links I've got on the info and post it into this response.

yep 100 percent correct

[Madhouse]

whoa, cool, thanks for the correction!  I had some bad info...

[98Z5V]

Here's a couple really good posts about it:

http://www.gunslot.com/forum/308-and-7-62x51-same-round

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

Also, there's a user here named "popgunner" (or close to that) - I've seen him post some of the best info about the differences, on another message board.  Hopefully, he'll see this and join the conversation.  <thumbsup>

[EdMP3006]

So basically......7.62x51 can be used in a .308 and the .308 CANNOT be used in a 7.62x51

[survivalshop]

So basically......7.62x51 can be used in a .308 and the .308 CANNOT be used in a 7.62x51

If you are talking about older barreled rifles , than yes . You also have to know that Fulton Armory brands all there barrels 308 , but say you can shoot one or the other.

Now there are some tight chamber 308's that may not like the 7.62 NATO type ammo .

Some manufacturers say not to shoot one or the other & not mix.( They also say not to shoot hand loads ,now that's a laugh , I wouldn't do much shooting )

To this day I have shot just about every 308 I have ever owned with both 308 & 7.62 & never had a problem .

Over thirty years of shooting and twenty of that I was a class I & III FFL .

[EdMP3006]

If you are talking about older barreled rifles , than yes . You also have to know that Fulton Armory brands all there barrels 308 , but say you can shoot one or the other.

Now there are some tight chamber 308's that may not like the 7.62 NATO type ammo .

Some manufacturers say not to shoot one or the other & not mix.( They also say not to shoot hand loads ,now that's a laugh , I wouldn't do much shooting )

To this day I have shot just about every 308 I have ever owned with both 308 & 7.62 & never had a problem .

Over thirty years of shooting and twenty of that I was a class I & III FFL .

The .308 i've built is using a DPMS chrome BCG and a DPMS 24" Chrome Bull Barrel.............upper and lower were stripped Iron Ridge Arms............so since its brand spanking new parts, I can shoot either one

[survivalshop]

Your DPMS barrel is probably stainless steel. I don't think DPMS makes a chrome lined barrel . I know a lot of people want them to.

You will have to try 7.62 to see if your build likes them . Some DPMS barrels have tight chambers for better accuracy & that will determan what you can & can not use.

[308reloaded]

98Z5V  thanks for the info. I will get a 308 barrel and not worry about it now..  not that I ever did.. I shoot both in my bolt gun , and before I sold my FNFAL to pay for this build I shot both, mostly 7.62 X51 surplus,  I did not know that it was the opposite of the 5.56,  to me that's all good news as I reload both.  never checked pressure as I just thought loads in book and not at max would be safe.

is there any data on what difference is  on different barrels  say 18" vs 24".  I am going will 24"  and will turn muzzle end for flash suppressor/ brake

[imschur]

7.62x51 - The word from DPMS

JonF a DPMS employee and the moderator of the DPMS support forum posted the info at the bottom of this post. The pdf was from a link on the DPMS forum

1533_.pdf

[imschur]

and another

[imschur]

Did anyone see the articles in Gun Tests on the 308 vs 7.62?

[Timing]

Actually not really. The 42k psi is incorrect. 7.62 measures 42k cup (copper unit of pressure) you can't compare numbers while ignoring units of measurement 42k CUP does not equal 42k PSI.

7.62 does measure less, but it is around a difference of less than 5k psi, not 20k.

[survivalshop]

and another

That is the factory covering there arse. They only put that out there because there is some non US mil spec fodder out there that has blown up rifles & want to cover them selves .

Just like reloads , cover the arse, if some one makes an over loaded rd. & blow the rifle up .

Now some one needs to till me how , you will get rapid throat erosion from a lower pressure 7.62 vs  the higher pressure 308 .

It is true with some non US 7.62 might have some COL differences & tight 308 chambers might not like them ( what DPMS chambers tight & rough ,naw ) , but bottom line is they are the same cartridge , period.

[98Z5V]

Info from the 303british.com article I posted:

Military ammunition is loaded to maximum average pressure 50,000 CUP (approximately 58,000 PSI using the modern piezo transducer method of measurement). This standard is used to ensure better consistency round to round. It is proofed at 67,000PSI. The ammunition can then be used in a wide variety of firearms with no ill effects.

Commercial ammunition has a SAAMI/ANSI maximum pressure of 62,000PSI. While not every manufacturer may load it to this level, this is the industry established maximum. This is also measured using the piezo transducer method. The proof cartridge pressure is 83,000 to 89,000 PSI. Note the differences between the military test and operational standard vs the commercial one.

[bgc]

Keep with the 7.62 in your gun.

American Eagle has a load made for the M1A that is 7.62X51. This round has performed well in my DPMS 7.62 barrel.

I am a firm believer in following the instructions from the folks that build the equipment.

[survivalshop]

So , that article is saying I can't shoot or shouldn't shoot comm. 308 in my 7.62 barrel ?

[98Z5V]

So , that article is saying I can't shoot or shouldn't shoot comm. 308 in my 7.62 barrel ?

No, brother - not necessarily.  The primary caution is with the older surplus military rifles.  Those are the ones that can have issues if you repeatedly shoot .308 Win through them. 

I'm a firm believer that if you have modern parts in modern builds, then it doesn't matter which rounds you shoot, or what is marked on the barrel. 

[survivalshop]

I was being sarcastic about that statement . Sorry.

But that brings up some thing else , if the comm. 308 is loaded , tested at a higher pressure than std NATO 7.62 , would not the higher pressure comm. ammo be more potentially dangerous to an older action ?

The bottom line is , its the manufacturers that are just covering there butts with those disclamers.

Shoot what shoots the best out of your particular rifle . We all know how some can be picky.

[Dusty44]

There is a factor about the length of the throat of the chambers and cartridges.  With some specific cartridges (brass)  as loaded by the particular manufacturer or with the shape and specific dimensions of the bullet in that load,  the 308 Win brass will extend slightly into the barrel throat of a NATO chamber.  When the cartridge is fired in that NATO chamber there is no place for the brass to expand to release the bullet and the resulting pressures can reach levels very far beyond any proof tests/standards.

This information has been published several times to my own reading/experience/recollection in technical articles and notations in several of the magazines I subscribe to,  including "American Rifleman."

[telluwhat]

Your DPMS barrel is probably stainless steel. I don't think DPMS makes a chrome lined barrel . I know a lot of people want them to.

You will have to try 7.62 to see if your build likes them . Some DPMS barrels have tight chambers for better accuracy & that will determan what you can & can not use.

I have a Bushmaster 308 ORC, it has a chrome lined barrel. It was my understanding that DPMS made these rifles for Bushmaster. Is this an exception to the rule or did DPMS make everything except the barrel? Thanks.