.308 win. the same as 7.62x51?

[CSestp]

Hey I learned (on this site) that 5.56 and .223 have small differences that make a big difference on the life span of you gun. Does the same go with 7.62x51 and .308 win.? Please explain or shoot me some good links.

Is all 5.56 considered 5.56 NATO? Same question for 7.62x51, is that 7.62 NATO? Or are there 3 types of each: 5.56, 5.56 NATO, .223. 7.62x51, 7.62 NATO, .308 winchester.

Thank you.

 

[Jim K]

The supposed differences between .308 Winchester and 7.62 NATO and between .223 Remington and 5.56 GI have been discussed ad nauseam, with heated arguments over a ten thousandth of an inch or a grain of powder.

For practical purposes, and in modern rifles (not reworked milsurp), there is no practical difference.

OK, I have committed heresy, so let the flames begin.

Jim

 

[CSestp]

Let me rephrase this then, with out opinion's and only with fact's please state the differences if any in 7.62x51, 7.62 NATO, and .308 winchester. Please cite all information.

 

[Onmilo]

Actually, the dimensional differences between the cartridges will not diminish the life of the gun that they are fired in.
The life of the cartridge case will be diminished if, say, a commercial .308 cartridge is fired in a NATO dimension 7.62X51 chamber.
This is also true of a commercial .223 case fired in a 5.56 NATO dimension chamber.
In other words, the chamber dimensions of a NATO chambered rifle run larger than the dimensions of a commercial sporting rifle chamber.

The maximum generated pressure curve generated by a NATO specification 5.56 cartridge is greater than that generated by a commercial .223 cartridge.
This is reversed in the .308 commercial verses NATO 7.62 cartridges with the NATO cartridges developing lower pressure curves than most of the commercial offerings.

The pressure curve of commercial full power large game cartridges runs higher than the NATO specification cartridges because these cartridges are loaded to near maximum to gain maximum ballistic capability when used for the hunting of larger and more dangerous game animals.

Most rifles meeting SAAMI proof specifications will handle the different cartridges on a limited basis but as a general rule, excessive pressures will show signs of such in individual rifles.
Again, in other words, If you are shooting 20 to 50 full power commercial cartridges in your NATO rifle for the purpose of hunting game animals and you are keeping your cartridge bullet weights in line with recommended bullet weights for the NATO dimension cartridge, in example, 150-168 grain weight for the 7.62X51, it is most unlikely your rifle will fail if it is designed and built correctly.

In that same general rule catagory, Semi auto military type sporting rifles chambered for .223 will accomodate 5.56 NATO dimension cartridges and .223 commercial dimension cartridges interchangeably, without issue.


Military type semi auto in 7.62X51 NATO should be used with NATO dimension cartridges when target and pleasure shooting where a large number of cartridges are fired.
There are few cartridges loaded to commercial standards that are recommended for these military style rifles for shooting in high volume applications, the higher pressures and thinner cartridge case wall dimensions can cause problems with function and reloading these cartridge casings after firing in a Military chamber can lead to case head seperation in a very short amount of case resizes.
Consequently, NATO dimension cartridges should not be fired in commercial style rifles regardless of action type.
The thicker case walls of the NATO dimension 7.62 cartridges tend to cause function problems in commercial rifles.

 

[Average Joe]

Here's my take. You can shoot Nato in a new commercial rifle.
You can't shoot commercial in a Nato rifle. Its the higher pressure in a commercial round that will cause problems.

 

[rcmodel]

It is interesting to note that if you reload 5.56, or 7.62x51 NATO, you do it using .223 Remington or .308 Winchester reloading dies.

No die manufacture makes sizing dies specific to the 5.56 or 7.62, because the cases are exactly the same outside dimensions as their commercial counterparts, the .223 & .308.

 

[SaxonPig]

Well, let’s see.

7.62 x 51 is 388.62 and that would 388.312 more than .308 so it doesn’t look like they are same.

But then, I was never very good at math so I just shoot military 5.56 and 7.62 interchangeably with commercial .223 and .308 in all of my rifles, both bolt action and semi-autos, without any noticeable differences. They all feed, chamber and fire just fine. I have never noted any significant difference in apparent power levels between commercial and military ammo and none of my guns have ever balked at any of it.

But then maybe I'm just kooky.

 

[Shade00]

Well, let’s see.

7.62 x 51 is 388.62 and that would 388.312 more than .308 so it doesn’t look like they are same.

But then, I was never very good at math so I just shoot military 5.56 and 7.62 interchangeably with commercial .223 and .308 in all of my rifles, both bolt action and semi-autos, without any noticeable differences. They all feed, chamber and fire just fine. I have never noted any significant difference in apparent power levels between commercial and military ammo and none of my guns have ever balked at any of it.

But then maybe I'm just kooky.

+1. The differences have been discussed back and forth for some time. I am of the opinion that .308 NATO and .308 Winchester are so close that there is almost no difference. Some time ago I read a very informative thread by a gentleman who was a commercial ammo tester. He made one excellent point: pressure numbers that folks use to argue the difference between the two often come from different pressure measurement systems. I wouldn't have a problem shooting .308 Win in an Enfield 2A chambered for 7.62x51 NATO.

 

[USSR]

It is interesting to note that if you reload 5.56, or 7.62x51 NATO, you do it using .223 Remington or .308 Winchester reloading dies.

No die manufacture makes sizing dies specific to the 5.56 or 7.62, because the cases are exactly the same outside dimensions as their commercial counterparts, the .223 & .308.

+1. No problems using commercial .308 in a modern 7.62x51 rifle as long as the commercial .308 is loaded with a similar weight bullet (~150gr).

Don

 

[CSestp]

Very nice fellas and mod can come along and close this now I found out what I needed to know.

On a side note, is there anyway we can sticky this along with a similar thread of .223 and 5.56. So people like me who are less informed on these matters don't have to ask every other week? Maybe start a ammo section as well?

 

[Lone_Gunman]

When people talk about differences in size, they forget sometimes that they are talking about the chamber size not the cartridge size.

The external dimensions of the cartridges are identical. If this was not true, you could not use the same reloading dies for either cartridge.

7.62x51 brass tends to be a little thicker, thus the internal dimensions are slightly less. This gives less volume for powder, and if you load a 7.62x51 case with as much powder as you would put in a commercial case, you might get a problem with over-pressure. This could be catastrophic.

With regards to chambers, the 7.62x51 chamber is a little larger. Also, the leade (the part of the chamber neck before the rifling starts) is also a little longer. This is to allow for more reliable feeding for semi and full auto guns.

Hope this helps

 

[Hostile Amish]

The calibers are the same, the pressures are different.

As a general rule, don't use .223 in a rifle chambered for 5.56, or a .308 in a rifle chambered for 7.62. Semi-automatics have more of a problem with this interchange than manual rifles.

 

[Harve Curry]

Correct me if I'm wrong but the way I understand it is:
Military chambers are larger then commercial chambers. This is to help reliablity in adverse conditions.

308 and 7.62 ammuntion are basically the same except for types of powder and the resulting pressure curve. The semi auto designs of military actions for 308/ 7.62x51don't lend themselves to slow burning commercial powders, to much pressure at the gas port. One exception might be the FN type rifles with adjustable gas ports, but you have to know how to use them.

223 / 5.56 can be used interchangalbly in sporting arms or military arms . The military actions it's used in can digest both commercial or military ammunition.

 

[jonnyc]

"Military chambers are larger then commercial chambers. This is to help reliablity in adverse conditions."

Yes, but not significantly so.


"308 and 7.62 ammuntion are basically the same except for types of powder and the resulting pressure curve."

No, they can use the same powders and have exactly the same ballistic and pressure properties. Old military pressure measurements and commercial pressure measurements were done using different systems of measurement. If done with the same equipment they are essentially identical.

 

[Lone_Gunman]

Old military pressure measurements and commercial pressure measurements were done using different systems of measurement. If done with the same equipment they are essentially identical.

That is true, but remember if you take a commercial 308 case, and a military 7.62x51 case, and load the exact same amount of powder, and seat your bullet to the same depth, the cartridge in the 7.62 case will have greater pressure.

 

[jonnyc]

That is true, but we are not discussing the interchangeability of reloadable cases, or even reloading in this caliber. Do not reload hot .308 loads into 7.62 NATO cases. However, I believe the original question concerned the interchangeability of factory loadings.

 

[Onmilo]

Reloading is exactly where the problems lie between military dimension and commercial dimension cases.
Thinner commercial brass that is fired in a more open dimension military chamber will expand more and this leads to work hardening when it is sized back to commercial dimensions in those afterformentioned die sets.
This leads to case splitting and case head seperation in a very small number of times reloadeding the case.

In addition to this, 5.56 Nato cartridges fired in a commercial .223 chamber tend to produce higher than normal pressure spikes because the thicker NATO dimension cartridge cannot expand enough.

SAAMI conducted pressure tests where NATO cartridges fired in commercial chambers were producing around 59,000 pounds of pressure per square inch in copper units of pressure.
Normally, commercial cases fired in commercial chambers will produce between 48,000 and 52,000 units of pressure.
Because of this pressure spike, SAAMI does not recommend shooting 5.56 NATO dimension cartridges in a commercial .223 chamber.

The good news for AR15 shooters is the majority of rifles are chambered with a 5.56 NATO dimension chamber with the exception of Match type barrels which tend to feature commercial minimum headspace dimensions.
Even Ruger uses the 5.56 NATO dimension chamber on their rifles.

Bolt action, single shots, and pump action commercial rifles are generally where most of the problems turn up using NATO dimension cartridges because of the commercial chamber dimensions featured on these rifles.

 

[Lone_Gunman]

The world would be a better place if the 223 chamber was eliminated completely, and replaced by the 5.56 mm NATO case.

No one would be any worse off, even 223 target shooters, and most people would be better off. There is nothing a 223 shooter/reloader can do that could not just as well be done with a 5.56.

 

[Onmilo]

I agree, standardization is a good thing.
When you look at commercial ammunition production, the thinner commercial brass is a good thing for their bottom line and this is, most likely, the main reason the .223 was standardized for commercial production.

 

[Gewehr98]

No sticky needed.

Just use the forum's search function.

The topic will come up several times in the large list of threads that hashed it out before this one.

It works like a charm, really.