7.62 NATO vs. .308 Winchester


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Lindenberger
February 14, 2006, 10:35 PM
I have some questions about how the 7.62 (.30 cal.) NATO can be used interchangably with the .308 Winchester. The .308 converts to 7.8232mm. In SAE, there's 8/1,000 of an inch difference; metrically, the difference is expressed as .2032mm. This seems like a whole lot of difference in the close tolerances of a rifle barrel. Can you shoot a .308 Win in a 7.62 NATO rifle?
What are the considerations? Can you shoot any old 7.62 NATO in a .308 Win? What would be the considerations there?

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MachIVshooter
February 14, 2006, 11:04 PM
.308 is the bullet diameter, which is in fact 7.82mm. Bore diameter, measured from land-to-land, is .300, or 7.62mm. Cartridge Nomenclature can get tricky, but generally speaking any Western cartridge designated .30 or 7.62 mm uses .308" diameter bullets. Lazzeroni, a proprietary cartridge manufacturer, does use bullet diameter in his labels, such as the 7.82mm Patriot or 7.21mm Firehawk.

Also, many cartridges nomenclature is not close at all to bullet diameter. .38 special uses .357" bullets, .38 ACP uses .355" bullets. .44 Mag uses .429" projectiles. It is important to know these details about any cartridge you may be using or loading for, as this practice of rounding numbers or keeping a name despite changes is commonplace in the gun world.

To answer your question, yes. 7.62x51mm NATO can be fired in commercial .308 Winchester chambers, and vice-versa.

joebogey
February 14, 2006, 11:22 PM
Although you can shoot the 7.62 X 51 in modern firearms, it's not always recommended that you shoot the 308 in weapons chambered for the 7.62 as the pressures in the 308 can be higher in the modern rounds.

ClarkEMyers
February 14, 2006, 11:23 PM
You're kidding right? That's not where the difference lies.

In .308 and 7.62X51 (and the .30-'06 and the .30-'03 and the .30-40) all (at least for all practical purposes) cases it is a nominal .30 bore and .308 groove. Remember there are non-standard rifling forms - e.g. Microgoove with larger bore and smaller groove sizes - and differences in measurement depending how far one chooses to carry the decimals.

Putting very much weight on the artificial conventions of naming gets pretty silly. FREX the .218 Bee, .219 Donaldson, .220 Swift, .221 Fireball,. 222 Remington, .222 Remington Magnum, .223 Rem, .224 Weatherby, .225 Win can all use the same bullets though the cases are quite different. It would be a great mistake to take the different numbers as meaning the bore and groove diameters must be different.

FREX .30-'06 and .308 Winchester refer to the same nominal bullet diameters one referencing bore size and one groove size. Individual bullets may be made oversize in hopes of better accuracy - some Lapua - and cast bullets generally run larger than jacketed.

In most cases (Lake City Brass :D ) any distinction is without a difference. However the SAAMI specs and the military specs are incommensurate and the military headspace is gaged differently and some military firearms run long chambers or have excessive headspace by SAAMI gages. Some non-military production, it's been reported of the Steyr Scout, may have long chambers in hopes of enhancing feed with military or just dirty and corroded cases or otherwise working better under adverse conditions.

Jerry Kuhnhausen in his gun smithing books, Clint at Fulton Armory and many more in print and on the web expand on all this in great detail with diagrams.

blackdragon
February 14, 2006, 11:57 PM
There is a FAQ posted at the falfiles forum showing extreme detail; between the two rounds -- there is a small size difference, and .308 is higher pressure.

However, that does not say if it is safe ot not.

Personally, I contacted my rifle's manufacturer (DSA) and asked -- they say all of their products are safe with either 308 or 7.62x51.

rero360
February 15, 2006, 11:06 AM
I've shot both out of my savage 11, and from my own personal experience it felt like the recoil was about the same for the two, however thats about as basic as you can get and there was probably a number of things different between the two types of rounds, all I know they both fed and fired reliably through my gun and it didn't blow up on me so thats a plus.

Grump
February 15, 2006, 02:32 PM
Okay, tell us the CUP pressure max's for each round. Make sure it's the same standard, mean average peak, or whatever.

Chamber dimensions are more generous in 7.62 NATO than SAAMI .308 Win, but I've never seen anything on AMMO dimensions. In fact, some sources like Fulton's website mention NATO surplus holding more consistently on CARTRIDGE minimums, headspace, than commercial .308 Winchester.

Theoretically, thinner/weaker/softer commercial brass of minimum cartridge headspace could be over-stretched in a way-long NATO chamber. When I was shooting min-headspace ammo in a mid-range headspace chamber, first fires were no problem, and cases broke at the 3rd-4th reload.

BBstacker
February 15, 2006, 06:52 PM
I shoot .308/7.62 out of my FAL. Military brass is thicker so if you reload you can not use the same amount powder.It is the same with the .223/5.56.

SMLE
February 15, 2006, 08:03 PM
Here is a very good essay on the subject.

http://www.smellysmleshooters.net/ammopressure.htm

Lindenberger
February 15, 2006, 11:11 PM
Thanks, guys. One can learn so much at this website.:)

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