7.62x51 and .308

Yep. Although the headspace specs are a little different, I don't think anyone is making 7.62x51 ammo that won't fit in a .308.

It's worth noting that you can't go the other way (.308 ammo in a 7.62x51 rifle). Many commercial .308 loads exceed the maximum allowable pressures for 7.62x51 rifles.
 
It's worth noting that you can't go the other way (.308 ammo in a 7.62x51 rifle). Many commercial .308 loads exceed the maximum allowable pressures for 7.62x51 rifles.
Click to expand...

I thought that was more an issue with 5.56 and 223...
 
With 5.56 mm & .223, it's actually the other way around - you can't use the 5.56 ammo in the conventional .223 guns because NATO 5.56 can have higher pressures than the .223 specs allow.

EDIT - As 73-Captain kindly pointed out to me in PM, there are .223 chambers (such as the Wylde) that are designed to safely fire 5.56 ammo as well as .223.
 
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The pressure curve of civilian ammo might be such that pressure at the gas port of a semi-auto military rifle would be high enough to cause damage to an operating rod. I rather doubt that the maximum pressure would be high enough to blow primers.

Brand-new civilian ammo will cycle through the military semi-autos, but the use of small-base dies in resizing for reloads is recommended for proper cycling.

A new case has a smidgen of clearance with the chamber wall. On firing, the brass expands to fill that and takes a set. If the case is not compressed by a small-base die, the next time the round is chambered there is no longer that smidgen of clearance. Upon firing, it is possible for the case to bind, slightly, and make extraction difficult.
 
I regularly shoot 7.62X51 NATO ammo in my Remington 700. Works fine.

THe reloading manuals treat them as essentially the same thing, too.
 
Perhaps I am all wet but before I purchased my FNAR, I done a good bit of study on .308 in a 7.62x51 chamber and the reverse. It's not about the pressure because they are measured in different areas. What does matter is the head space regardless of which one goes to what.

Reloads are apparently where folks may get into trouble. My limited study proved to my satisfaction that factory brass will shoot either way. Since I'm not into reloading anymore, I got my FNAR and have enjoyed some fantastics groups with both 7.62 and .308 ammo.

My preference is the lighter 147 to 168 grainers and have not witnessed any flattened primers or stretched necks whatsoever. Early on I was quite nervous and checked every round... twice. Hardly even consider it anymore but I still shoot factory rounds and sell my brass for discounts on handgun ammo.

Been about a year and my groups have actually improved, however, I'm still waiting to fall into the 1/2" cloverleaf club. Ain't happened yet. :cool:
 
I know this will seem like a silly question, but when you talk about 7.62mm x 51 or 5.56 the 7.62 and the 5.56 are in reference to bullet diameter and the other number (51) is the length right?
 
Correct.

That's based on mm, and is the European method of designating cartridges. Example, the Moisin Nagant shoots 7.62X54R, meaning a rimmed cartridge 7.62mm diameter by 54mm length.
 
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Sorry to thread hijack, but it's somewhat similar ;)

I know 7.62 Nato gauges and .308 are differant, but looking at the "General" specs of them...

If a .308 field reject gauge doesn't fully chamber in a 7.62X51 weapon....that gun is "Within spec" isn't it? I know that some .308's will disappear in 7.62's and still be safe...just wasn't sure...
 
poppycock

they are one in the same YOU can interchange safely ,the identical 308 win is the 762x51mm and vers vica,there is a lota bull floaTING AROUND the round was developed at high chamber pressure 50,000 to 60,000 in an attempt to duplicate 30 06 performance,with less brass,some 762x51mm are down loaded for automatic fire,cetme rifle,although some spanish loads top 2900 fps with a 147 grain pill:eek: I have fired lots of commercial 308 w thru 7.62x51mm rifle with no problems.:cool:
 
All of my 7.62x51 brass weighs about 182gr, and my .308 brass weighs 10gr less.
... or just get a gun that shoots .30-06 and call the dispute over:rolleyes:
 
.308, according to SAAMI spec, has a tighter headspace requirement than 7.62x51. A long-headspaced 7.62x51 can still be good, while a long-headspaced .308 is not considered good.

The reason for this is that .30 caliber machine guns require more forgiving tolerances when going through high volume in dirty environments. So, the chamber dimensions allow for a few thousandths of slop.

Both cartridges overlap with optimal headspace of 1.631 to 1.635 inches. If your rifle's headspace measures between these two numbers, it will shoot either cartridge interchangeably.

The only other consideration is the burn rate of the powder and the weight of the projectile. Gas-operated semiautomatic 7.62 rifles will expect a projectile under 180 grains, and a powder burn rate in the middle of the road... ultra-slow burning powders typically used for long barrels and heavy projectiles are not safe in a semiautomatic 7.62 rifle.
 
andrewstorm, a little history: When the .308 was first put on the market, the factory data showed a pressure of 55,000 psi. Factory data on the '06 was generally about 49,000 psi--due to the gazillions of old rifles in existence. It was not until the factory introduction of a 110-grain loading in the '06 that a pressure of 53,000 to 55,000 psi was shown.

In the early years, with 22" barrels and 150-grain bullets, there was zilch for practical difference in performance between the two cartridges.
 
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