7.62 vs. .308 Winchester in sporting arms

[xd45gaper]

ok in regards to gripperdogs last post, and the article in american rifle or whatever it is lol got me thinking last night after i read it. if the 5.56 and .223 are interchangable in firearms marked 5.56 but not in firearms marked .223

does the same hold true for the .308 winchester round? I have an older model 70 featherweight in .308 and have on several occasions almost bought mil surp ammo for it for just shooting at the range but didnt because of the 5.56 being loaded at higher pressures for the military.

so would it be safe to shoot mil surp ammo out of a firearm marked .308 winchester? and dont go off on the defenition of sporting arms i know you can hunt deer with a FAL or any other military style rifle but they where not designed to do so.

 

[nalioth]

Ah, again this question arises. (the search function must be broken on a whole lot of boards)

Here is some food for thought:

http://www.surplusrifle.com/shooting2006/308vs762nato/index.asp

http://www.fulton-armory.com/308.htm

http://www3.sympatico.ca/shooters/7_62vs308Pt2.htm

Okay, the big question, the question that always comes around…

7.62mm NATO vs. .308 Winchester

The same?

In a nutshell. No. Maximum pressure ratings for the two are not the same, the NATO round is rated at 50,000 psi (Cartridges of the World, 9th Ed). The .308 commercial is rated at anywhere from 52,000 to 62,000 psi depending on the source of the information. Even the units and methods of testing are not the same.

The idea here is this. The FR7 and FR8 were designed to shoot the 7.62 NATO round, not the commercial .308 round. If you reload, you can easily keep your loads below the max. If you want to shoot mil surp ammo, use NATO approved rounds. If you want to use commercial loads…DON’T.

Also, if you reload for this rifle and use military brass, do note that nearly every reloading manual out there recommends reducing loads because military brass has less internal volume because of thicker walls and bases.

Of course, this entire issue is still dependent on the condition of your specific rifle.

I have gone so far to make sure that when I reload .30 caliber ammo, I mark it as “7.62 NATO” or “.308 Win” depending on which brass, load and rifle I loaded it for.

 

[gipperdog]

The simple answer is - No. They're different like the .223 & the 5.56 NATO
But "technically", there are actual chamber differences between the .308 & the 7.62 NATO.

Here's a few sources regarding this -
http://www.thegunzone.com/30cal.html
http://www.fulton-armory.com/308.htm
http://www.smellysmleshooters.net/ammopressure.htm

 

[30Cal]

7.62mm in a .308Win chamber (which is a tad bit shorter) should be fine. If you can get the bolt closed (which you will), you should be good to go.

The potential problem arrises when you put commerical .308Win ammo in a 7.62mm chamber with long headspace. The commercial brass is thinner and may separate.

 

[trueblue1776]

Functionally I think they are the same, any actual evidence otherwise and I may reconsider, until then...

I think for the most part the difference is academic, I don't know any FAL, G3, CETME, or M14/M1A guys who are afraid of running commercial ammo in their guns.

Military guns are usually built pretty tough, I don't worry.

 

[W.E.G.]

This question has been asked thousands of times on the internet.

So far, I am aware of NOBODY who has suffered damage or mishap simply from firing commercial .308 ammo in a gun marked 7.62x51.

Even the hottest .308 ammo is far below the proof pressures for 7.62x51.

If a rifle has bad headspace it doesn't matter whether its marked .308 or 7.62x51. Either choice could be an element in a mishap - but not because of the ammo choice. If you don't know the headspace of your rifle, you should stick to shooting only current-manufacture, brand-name ammo marked the same as the rifle. At least then if it blows up, you won't have the excuse of saying the cause must have been "wrong ammo."

Most milsurp 7.62x51 ammo is loaded with a bullet in the 145-150 grain weight class. If you jack up the bullet weight and jack up the powder charge in 7.62x51 milsurp rifles, you might start stressing components, and accellerating wear. At a dollar-a-shot or more these days, I don't think there is any reasonable likelihood that anybody will ever find out how many conventional .308 rounds in a 7.62x51 it takes to demonstrate anything worth reporting.

My rifle team busted some M14 and M1A receivers (cracked at the rear where the bolt slams into the inside of the receiver) by shooting hot 190 grain handloads. Very hot. Other than that, there are no issues I know of - and I would know.

 

[eldon519]

Even if a round is below proof pressure, it can still cause drastically increased wear on a part.

The level of stress imposed on a part is closely related to the logarithmic value of cycles it can endure. What that means is you'll be changing the life of your firearm by powers of ten, now a set number of firings. For a lot of materials, a 20% increase in stress is about enough to change the life of a party in cyclic stress by a power of 10. Max pressure for .308 is about 20% higher than for 7.62. That would mean a rifle barrel capable of handling 100,000 rounds without failing would be good for 10,000; a 10,000 round life might become 1000; 1000 might become 100. It'll probably be more than you'll ever need either way, but there are alot of other factors at play.

I don't know how many rounds a barrel can last without rupturing it, but it is worth noting that higher pressure comes with significantly higher part wear.

 

[trueblue1776]

I don't know how many rounds a barrel can last without rupturing it, but it is worth noting that higher pressure comes with significantly higher part wear.

rupturing? a bit dramatic??? You may burn your rifling in 5000 rounds instead of 7000, I'd eat my hat if anybody ruptured a barrel because of 7.62 NATO instead of .308 Win.

 

[eldon519]

Well that's what I was getting at. You're likely to burn out your barrel first, but rupture is possible. Containing the pressure is largely a matter of hoop stress afterall, and that is how something in hoop stress fails.

 

[Dave R]

If the differences are so great, why do the reloading manuals treat them essentially the same?

 

[USSR]

...why do the reloading manuals treat them essentially the same?

Because the cartridges are essentially the same; the difference is the slight difference in allowable chamber dimensions.

Don

 

[Nameless_Hobo]

Anyone know why the two cartridges are made different?
Seems to me that the military being able to use commercial cartridges may come in handy in the event of a military invasion, which was possible what with the Solviet Union existing at the time of the 7.62/.308's birth.

 

[trueblue1776]

Hobo,
the military has more ammo than they could possibly use in 500 years, I used to have to count it. The have reserves, just like their fuel reserves, that will never run dry.
I have been issued ammo that was made 20 years ago, think "rotating stock".

 

[W.E.G.]

I guarantee you, the military 7.62x51 guns can swallow all the
commercial .308 Winchester you want to feed them.

 

[ROMAK IV]

Military rifles chambered for 7.62 x 51, allow for longer headspace, that's it. 7.62 x 51 generally has thicker brass in order to allow the safe firing in the longer allowable chamber. That's also why 7.62 x 51 is genarally "annealed" in that area. Check your headspace with a commercial gage, the shorter one, and you should be fine. I would think there is more of an issue with softer primers than the actual caliber.

 

[xd45gaper]

so the commercial rounds actually have more pressure or no one knows because they are tested diffrent? i guess ill stick to commercial rounds i have never ever seen this topic disscussed. now the 223/5.56 i have

thanks for the links im going to read up some more on them

 

[Andrewsky]

Hobo,
the military has more ammo than they could possibly use in 500 years, I used to have to count it. The have reserves, just like their fuel reserves, that will never run dry.
I have been issued ammo that was made in the 20 years ago, think "rotating stock".

That sounds about right. Isn't there about 180 ammunition factories in this country? The largest one, Lake City, turns out 4 million rounds a day?

 

[buttrap]

Tried to run a case of Rem .308 thru a M-60 once and It did not run one round correctly at all. In fact it was a bit scary to a degree.

 

[eldon519]

so the commercial rounds actually have more pressure or no one knows because they are tested diffrent? i guess ill stick to commercial rounds i have never ever seen this topic disscussed. now the 223/5.56 i have

Maximum pressure for .308 is 62,000 psi per SAAMI specs. 7.62x51 NATO is loaded to 50,000 psi. I do not know if they are measured the same or not though. 7.62 NATO may use the neck transducer method like 5.56 NATO. I do know that 2750 fps for a 147-150 grain bullet is pretty consistent with .308 reload data limited to 50,000 psi though.

 

[cpttango30]

In my 8 years in the army I tried my best to run the army out of ammo.

My platoon held a M249 (SAW) range and had more than 100,000 rounds left over. I took 40,000 and linked it all together and just held the trigger on my saw (That was almost as fun as s*x) untill I tried to clean Betsey the barrel would not come off. Turns out that I got her a little hot under to collar . I got a good butt chewing from the CO but he confided in me that he had done the same thing to once nad it was a freekin blast.

I have burried so much stuff for the military too. I have burried the sealand containers full of kevlar helmets, MOPP Gear, Web gear, PRO mask, and some stuff that they would not tell us what it was.