(Stupid) question re: 7.62X51 vs .308

[ARCHIVED THREAD] - (Stupid) question re: 7.62X51 vs .308

Posted: 12/1/2001 5:30:06 PM EDT

Is it Kosher to shoot 7.62 X 51 in a gun marked .308? I only ask because I know 5.56 in a gun marked .223 is generally a no no and wondered if tit was the same for 7.62/.308 Thanks!
Pit

Posted: 12/1/2001 7:29:31 PM EDT

[#1]

No problem to shoot 7.62x51 in a gun chambered for .308.

If anything, the reverse could be the problem (for example, hot commercial .308 does not run well in an M1A). SAMMI spec for max pressure in .308 is about 12,000 CUP higher than the spec for 7.62x51.

Posted: 12/1/2001 7:39:56 PM EDT

[#2]

Cartridge dimensions are different also.7.62x51 is a little bigger if I remember correctly.

Posted: 12/1/2001 7:47:49 PM EDT

[#3]

I know everyone keeps linking to all these SAAMI sites as God's Bible to ammo, but it has been my experience with the ammo and guns I use and have used that .223 and 5.56 are English and Metric equivalents of each other. Nearly every current production AR-15 that I've seen says .223/ 5.56 on the side of the receiver. The same is true for 7.62x51 and .308. It's basically the same stuff.

I'll now invite those on the board who are stuck up know it alls to tell me how SAAMI is the all knowing and that I don't know jack about jack. (I really don't ya know)

Posted: 12/1/2001 8:53:24 PM EDT

[#4]

I always thought that 7.62x51 and .308 were just the metric and imperial names for the EXACT same cartridge (that can of course come in different loads, like any other cartridge).

Posted: 12/2/2001 4:49:18 AM EDT

[#5]

Those that use SAAMI as the bible, are still listening to their 8 Track, driving their Biscayne (with the factory tires), and are sure thet their butterflied collar shirts are going to be back in fashon this year.

7.62 NATO, and 5.56 NATO vs. .308 Winchester and .223 Remington. Standard vs. Metric.

Yes, there are small diferences in the throat dimensions.

For the most part you may interchange metric vs. standard ammo. Their are a couple of exceptions, such as 7.62mm machine gun ammo(linked/delinked) that just does not like the slightly smaller chamber/throat of the .308.
The same is true of several 5.56 NATO machine gun stuff.

The pressures that SAAMI provides are "tuned" for the weakest possible rifles.

Sorry to ramble, but, SAAMI just makes me angry.

Yes you can shot (most) 7.62 out of a .308

Lew

Edited, cause I spelled SAAMI wrong....

Posted: 12/2/2001 5:12:27 AM EDT

[#6]

What Lew said -
with the caveat that some commercial 308 loads with heavy bullets may be loaded with powders with slow enough burning rate to put a strain on the M14 gas system. The op rod of M14/M1A rifles isn't as long and flexable as the M1 Garand's, but high port pressure is still kinda rough on the rifle.

Posted: 12/2/2001 5:25:53 AM EDT

[#7]

Much ".308" is converted 7.62mm NATO.

Conversion is done by the highly technical process of slapping ".308 Winchester" labels on boxes of 7.62mm ammunition, nothing more.

Look at any of the large ammo sales websites and try to find 7.62mm NATO -- pretty hard to find. Lots of surplus "military .308" (an oxymoron is there ever was one) though. No one's blown up a ".308" rifle with this stuff yet.

Same conversion from 5.56mm to ".223" of course.

-- Chuck

Posted: 12/2/2001 5:55:19 AM EDT

[#8]

You won't typically run into problems unless you try using quetionable 5.56 NATO surplus in really tight .223 WIN chambers (questionable surplus in any chamber is a bad idea).

Would advise againt using stuff like Hornady Light Magnums in 7.62 NATO chambers (particularly FALs and M1As... HK91s seem to be ok with it, the case will just be beat to hell and back)

Posted: 12/2/2001 3:34:44 PM EDT

[#9]

First, its SAAMI.
Anyone that builds ammo based on what they know themselves deserves what they get. If you load heavier than published data and the receiver blows on you...its "I told you so".
7.62x51 is a different cartridge than .308 Win!

Benchrest Central.com
A 3" group rifle is used as a jackhandle there.

Posted: 12/2/2001 4:27:22 PM EDT

[#10]

Where is SAAMI's data for a heavy-barrel AR15?

I'd like to see that. Both the 5.56 NATO, and the .223 Remington.

Lew

Posted: 12/2/2001 6:10:26 PM EDT

[#11]

The difference is that 7.62x51 cost $25 for 140 rnds. .308 cost $9 for 20. One is 18 cents a round the other is 45 cents a round. Big difference!
GG

Posted: 12/2/2001 6:34:26 PM EDT

[#12]

DavidC...What is SAAMI max for .308 versus 7.62?
I thought .308 was around 52,000. Maybe 55,000.( no book nearby to look it up) 12,000 less for 7.62 x 51 seems way low...thats like 30/40 Krag pressures. Help me out here

Posted: 12/3/2001 9:41:06 AM EDT

[#13]

andrew:

According the book Cartridges of the World by Frank Barnes, the SAAMI maximum for the Winchester .308 is 62,000 psi and for M59 7.62mm NATO Ball ammunition it is 50,000 psi.

FWIW....Geno

Posted: 12/7/2001 2:25:25 PM EDT

[#14]

To know more about this subject than you wanted to know, check out this thread on the FAL Files:

http://www.l1a1.com/cgi-bin/forums/ultimatebb.cgi?ubb=get_topic&f=13&t=000187

Posted: 12/7/2001 4:18:15 PM EDT

[#15]

The "English" system is used in the USA.
The "Metric" system is known world wide.

Posted: 12/7/2001 6:00:22 PM EDT

[#16]

Hot loads with heavy bullets and slower burning powder should not be used in gas guns, and can cause damage to the gas/recoil system. These loads are usually marked "Bolt Rifles Only." An example of these are the Hornady Light Magnums.

-Troy

Posted: 12/7/2001 6:15:31 PM EDT

[#17]

Now just a minute, yes they are the same round, but I had a Chevy Biscayne, a 1960 it was metallic violet, 289 V8, sweet car......oh sorry it was ammo...military term only they are not as tight so they shoot more reliabily, although not as accurate as a good bolt action.

Posted: 12/7/2001 6:54:22 PM EDT

[#18]

No, they are not the same.

See this url home.sprynet.com/~frfrog/miscelld.htm#same%20round

Q. Are the 7.62 x 51 mm NATO rounds and the .308 Winchester really the same round?

A. Well, er, ah umm--kinda. The cartridge cases themselves are substantially identical with the exception that the NATO specification rounds (those marked with the NATO "cross in circle" mark) have substantially thicker cases than the commercial variety. They are thus able to withstand stretching better when fired in loose chambered military weapons (done for reliability purposes).

The NATO specs for the cartridge case reference different datum points for some measurements but these can be interpolated. Base diameter specifications .2" from the base of the rim are approximately .4706" - .006" for NATO specifications and .4703" -.008" for SAAMI. The specifications for the diameter at the shoulder of the case is difficult to compute as it is at the intersection of two datum lines but would probably be slightly larger than the SAAMI specification of .4540".

The GI chamber has a shorter (.1563" vs. .1050" SAAMI) and non tapered bullet seat, a slightly less tapered throat, and more generous diameter tolerances, (.4730 + .002 (interpolated at the .200 reference line) compared to .4714 + .002 for SAAMI. I am working on drawings and will post them when available.

The headspacing requirements for the NATO chamber is much more generous than that of the SAAMI commercial (.308 Winchester) specifications as can be seen in the table below.

Gauge .308 Win 7.62 MM NATO 7.62 MATCH
GO 1.630 +.002 1.6355 +.0005 1.6355+.002
NO-GO 1.634 1.6405 +.0005 1.6385
Field 1.638 1.6455

Q. Are the 5.56 mm NATO rounds (and M193 types) and the .223 Remington really the same round?

A. This is another of those "Well, er, ah umm--kinda" items. The cartridge cases themselves are substantially identical with the exception that military and/or NATO specification rounds (those marked with the NATO "cross in circle" mark) may have thicker cases and are thus able to withstand stretching better when fired in loose chambered military weapons (done for reliability purposes). Once again, the chamber dimensions are where the brown stuff impacts the rotating air dispersion device.

Commercial SAAMI specification .223 chambers have a much shorter throat, a smaller diameter bullet seat, and less freebore than the military chamber. When military specification ammunition is fired in a SAAMI specification chamber chamber pressure can increase dramatically--sometimes up to 10,000 psi. While this should not cause any problems in modern well made rifles it should give one pause. Conversely, SAAMI specification commercial ammunition when fired in a military chamber gives significantly lower pressures and velocities. See the drawing below for the details.