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Old January 23, 2008, 00:30   #101
Uncle Buck
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In the February 2008 issue of American Rifleman, page 20 , the editors deal with the ".308 vs 7.62, what's the difference" question. They say:

"Unlike using 5.56 x 45 mm NATO ammunnition in .223-chambered guns, which the Sporting Arms and Ammunition Manufacturers Institute (SAAMI) lists in its "Unsafe Arms and Ammunition Combinations" there is no such blanket prohibition on using .308 factory ammunition in 7.62 x 51 mm rifles or visa versa"

They also state:

"Also, military 7.62 x 51 loads can be encountered that exceed SAAMI's .308 Win maximum pressure of 62,000 psi."

So here is another claim in print that 7.62 ammo may be loaded to pressures higher than .308. This is just the opposite from what you hear in the net rumor.
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Old January 25, 2008, 00:28   #102
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is 308 safe in an L1A1? I've used SB without issue
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Old January 25, 2008, 09:35   #103
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Quote:
Originally posted by blameitonfinland
is 308 safe in an L1A1? I've used SB without issue
As stated above by SAAMI and American Riflemen technical writers....the rounds are interchangeable. The use of .308 should not present you with any new safety issues at all.
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Old January 27, 2008, 23:22   #104
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thanks
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Old March 25, 2008, 03:35   #105
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I love this thread!
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Old April 11, 2008, 07:46   #106
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I have been discussing this with a guy I work who is dead set against shooting factory 308 in 7.62 guns. He is claiming that it is the pressure put on the gas system parts due to the different powder. He is saying that the burn rate on factory is faster than military, thus, causing excessive pressure in the gas sysyem. Is there anything I can tell him that will rufute that?
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Old April 11, 2008, 07:56   #107
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Quote:
Originally posted by jkeen579
I have been discussing this with a guy I work who is dead set against shooting factory 308 in 7.62 guns. He is claiming that it is the pressure put on the gas system parts due to the different powder. He is saying that the burn rate on factory is faster than military, thus, causing excessive pressure in the gas sysyem. Is there anything I can tell him that will rufute that?
The powder in .308 Win ammo may well be "faster" burning than that in 7.62NATO ammo......it may well be SLOWER. Various burn rate powders are used to load 7.62NATO as well. You and I (and your friend) do not know which powder is selected to load any given lot of ammuniton.

His statement is somewhat a mistruth....as a SLOWER powder is the one which will give you a higer gas port pressure and strain the function of a semi/full auto gas powered weapon. That said...only the "Light magnum" .308 Winchester factory rounds would have a powder slow enough to cause much concern. I think these rounds have a cautionary warning on the box....maybe that is where your buddy got his 'education' on this subject.
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Old April 11, 2008, 16:52   #108
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Powder burn rate tables are not to be trusted as a reference source, see any reloading manual for confirmation of that.
Also powder is a propellant, not an explosive why does this matter? Because powder burn rates vary with pressure, that's why they are called "Progressive" powders.

If he doubts that trickle a 4" long line of powder on a hard, non-flammable surface & light it. Fizz, fizz, but no BANG! then just say "Is that a fast, or slow powder?"
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Old April 15, 2008, 20:30   #109
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NATO has recently updated their standards for 7.62 x 51 according to NATO AC/225 (LG/3-SG/1) to EPVAT testing.

The new standard now uses a Kistler 6215 Piezoelectric Transducer gauge and has a maximum pressure of 60,190 PSI (as opposed to 50,000 PSI CUP).

http://en.wikipedia.org/wiki/NATO_EPVAT_testing

This is much more comparable to the SAAMI and CIP pressure specs. The ammunition hasn't changed, just the type of gauge and the pressure specs. Now you can compare apples to apples.

UB
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Old October 15, 2008, 23:43   #110
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So why any difference at all between x51 and .308 using the piezo transducer?

The old x51 CUP figure was less than the SAAMI .308 CUP figure ostensibly due to the different locations and methods of mounting the copper crusher to the chamber.

So is there a difference then in how NATO attaches the piezo transducer versus how SAAMI does it? I know that 1,810 PSI isn't much, but the fact that there is a difference still makes one wonder a little bit if NATO rifles are not as strong as .308 rifles. Sometimes, the devil is in the cumulative wear on parts, not just in a sudden catastrophic failure.

I'm a convert and think it's OK to shoot .308 in a good x51 chamber, but it's still a little disconcerting that no one in the ammo industry seems to be willing to take a stand. I suspect that there's some uncertainty there as well and they aren't comfortable endorsing the use of their ammo in milsurp rifles.

I'm starting to look at this more like the +P issue with .38's. Some modest use of .308 is OK but a steady diet might loosen things up a bit?

Thoughts?
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Old October 16, 2008, 05:55   #111
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After a couple of thousand rounds of both I'm finding no appreciable wear.
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Old October 30, 2008, 12:48   #112
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Quote:
Originally posted by JamesTheScot
So why any difference at all between x51 and .308 using the piezo transducer?
It could be a number of things:

1. A real difference, but still not a very significant one.

2. A definition difference. Some use maximum pressure for individual cartridges, while others use a "maximum average pressure", where the maximum is averaged over a number of individual measurements, some of which are above and below the average.

3. Gauge difference. NATO uses the same gauge and measurement methods as the European CIP standard and the pressure maximums are exactly the same for NATO and .308 CIP.

The apparent difference between NATO and SAAMI (approx 2%) is not of the same magnitude as the difference between +P and standard pistol ammo which is more like 10%.
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Old November 02, 2009, 22:40   #113
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However complex, I'd have to side with the fact that the pressures are "essentially" the same. The greater issue still may be the headspace. Do you suppose a visual inspection of a commercial .308 Win case from a 7.62 chamber would reveal any distortion or other signs of distress?
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Old November 03, 2009, 06:22   #114
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Not with any of the 1,000s I've fired.
Visually you won't see a darned thing, the difference is way to small to be visually aparrent. I've used the Stoney point gage with a caliper & can't find diddly either.
In reality the chambering & extraction process is violent enough to hide the thoeretical differences between the two as the stretching & re-headspacing on chambering is bigger than the difference!
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Old November 03, 2009, 22:11   #115
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Soo . . . I'm thinking the Comm. .308 cases just won't stand up to the reloading as well . . .(?)

I've been casting about on the +P .38 analogy since I often carry a snubby and have (probably) overshot it too many times with +P.

Best I can figure, the pressure differences we're seeing with .308 and 7.62 may be 3% (at most). But +P .38 is at least 10-12% over MAXIMUM pressures. It is more like 60% over standard pressures.

The +P .38 thing is admittedly off-topic, but since the analogy was cited, I think it fair to level the playing field.

The difference between .308 Win and 7.62x51 pressures are minuscule compared to standard .38 special and +P.
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Old November 04, 2009, 11:59   #116
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Soo . . . I'm thinking the Comm. .308 cases just won't stand up to the reloading as well . . .(?)
In something like a FAL the cycling process beats up the brass so much that's the limiting factor for either case. When I reloaded both for a bolt action I could get 10~12 loads out of either. It seems to be a question of itty-bitty differences in headspace, once you've resized once to the "correct" headspace the wear is limited so there isn't much difference really.

Which bring on the thought that if this made a real difference you'd be able to buy either 7.62, or .308 Win. dies, & for some reason you can't maybe another indication of the difference being thoeretical only.
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Old November 04, 2009, 20:25   #117
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Good point on the dies!

I don't guess my M1A would beat up brass any more or less than an FAL (?)
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Old November 04, 2009, 20:56   #118
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More like differently
My M1a put a diagonal mark on rounds 1 thru 19, it didn't look as bad as the creased necks of the FAL, but it did shorten case life. ON the bright side round 20 was cherry
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Old October 07, 2014, 11:35   #119
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The question of “is it safe to shot 308 win in a FAL/L1A1 chambered to shot 7.62X51 has become one of the most perplexing queries of the shooting world. Just look at this thread, it was started in 2001 and still there’s no agreed answer on what is a serious question of safety

For my L1A1, I’ve decided to shoot only 7.62x51.

And for those of you who are bored and looking for something to read, here are my reasons why.

1. Because 7.62x51 is what the rifle was designed and built to shoot

2. 7.62x51 ammo is easy to find and buy

3. The chamber of a rifle designed to shot 308 is of different dimensions then the chamber of a rifle designed to shot 7.62 NATO

4. The 7.65 NATO cartridge and 308 win cartridge are different sizes

5. Although many folk do shot 308 in their FAL/L1A1, and there doesn’t seem to be any horror stories on the net of a L1A1/308 ammo combo exploding into little pieces, killing everyone in a 10 yard blast zone… My L1A1 was made about the time Kennedy issued the challenge of going to the moon. Although the gunsmith gave her a clean bill of health, I’ve no idea the number of/and type of rounds the rifles has fired in the 5 decades before I bought it. So, why take changes?

Last edited by Lastchip; October 07, 2014 at 15:48.
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Old October 07, 2014, 14:37   #120
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Quote:
Originally Posted by Lastchip View Post
The question of “is it safe to shot 308 win in a FAL/L1A1 chambered to shot 7.62X51

3. The chamber of a rifle designed to shot 308 is of different dimensions then the chamber of a rifle designed to shot 7.62 NATO

4. The 7.65 NATO cartridge and 308 win cartridge are different sizes

?
Re# 3: of course, the Military chamber is maximized for reliability...the sporting chamber is maximized for accuracy. Neither chamber rules out the use of the other named cartridge.

Re# 4: Different sizes? What are you talking about?? They are the same, die sets are the same, etc!
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Old October 07, 2014, 15:44   #121
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And a pleasant “Good Morning” to you Sir.

Here are links to the dimensions to the cartridges. If this information is wrong and you know the correct data. Wikipedia is an open source database, you can submit changes.

http://en.wikipedia.org/wiki/7.62%C3%9751mm_NATO

http://en.wikipedia.org/wiki/.308_Winchester

As you were kind enough to confirm, the chambers of the two rifles are of a different size. To me, if it’s available, which it is. I’d use the ammo designed for the rifle I’m shooting.

I also found this to be interesting reading

http://www.fulton-armory.com/%5Cfaqs...FAQs%5C308.htm
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Old October 07, 2014, 15:54   #122
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Some peeps allow themselves to get worked up about a whole lot of nuthin it seems to me..
They are for all intents the same but hey ifya want to limit your ammo to x51 feel free...

What happens to x51 brass run through a .308 sizing die?

BTW, how many Navy M1's in .308 do you see around?
I've only seen one in the last 20 years so I'm thinking that comparison is relatively meaningless..
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Old October 07, 2014, 15:57   #123
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Lastchip -

Here's the bottom line:

FN made rifles marked ".308 Match" for rifles on their way to the United States. Those same exact rifles were marked 7.62x51 for the Euro and other contracts. No practical differences.

Yes, we know the case volume in the military rounds is slightly smaller due to the thicker webbing spec in the NATO and other rounds. Reload accordingly. Meanwhile...

our own Uncle Buck, an engineer who was employed (iirc) by Uncle Sam in small arms/ordnance has written exhaustively here. You, too, can use the Search function. It comes down to the fact that the units "PSI", and "CUP" are not even close to comparable, and the 50,000PSI vs. the 62,000 CUP (or vice versa) are not even measuring the same things. Here's an important thought exercise:

Take your rifle out to the range. Shoot the .308 of your choice at your target at 200 or 300 yards. Mark the holes. Shoot the 7.62x51 of your choice at the same target. If the pressures differed significantly, you'd see significantly different elevations for the two ammo types.

You won't.

Edit to add: I see that Uncle Buck is up above in post 109 (among others) pointing out the pressure gauge standards and other things.
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Old October 07, 2014, 16:03   #124
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Quote:
Originally Posted by Lastchip View Post

For my L1A1, I’ve decided to shoot only 7.62x51.

And for those of you who are bored and looking for something to read, here are my reasons why.

1. Because 7.62x51 is what the rifle was designed and built to shoot


No.

The rifle, as demonstrated by the stampings on IDENTICAL rifles headed for the U.S. domestic market from FN (those people who "designed and built" the FAL), is intended to shoot both - because they are, for all intents and purposes, the same thing.

Go look at an FN imported to the U.S. See what you see on the barrel. Hint: there is no 7.62x51 on there at all.
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Old October 07, 2014, 16:20   #125
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Originally Posted by Lastchip View Post
And a pleasant “Good Morning” to you Sir.

Here are links to the dimensions to the cartridges. If this information is wrong and you know the correct data. Wikipedia is an open source database, you can submit changes.

http://en.wikipedia.org/wiki/7.62%C3%9751mm_NATO

http://en.wikipedia.org/wiki/.308_Winchester

As you were kind enough to confirm, the chambers of the two rifles are of a different size. To me, if it’s available, which it is. I’d use the ammo designed for the rifle I’m shooting.

I also found this to be interesting reading

http://www.fulton-armory.com/%5Cfaqs...FAQs%5C308.htm
Just passing through to see if this dead horse has been beat enough and see apparently not!!

Lastchip, using your links....

Read in the column to the right side of the page under "specifications", each cartridge listing has a maximum pressure listed. For the 7.62X51mm it is
60,191 psi for the .308 Winchester it is 60,191 psi.

Wiki also lists the parent cartridge of the .308 as the 300 Savage, while listing the parent cartridge of the 7.62X51mm as the .308. Wiki also lists both cases overall case length as 2.015 inches and then list them slightly different in mm, 51.18mm and 51.2mm

You can shoot whatever you want through whatever rifle you want and unless you make the news, we probably won't know... but the .308 and the 7.62x51mm are the same.

The Fulton Armory article is they are "talking" about chamber sizes of the weapons you are using more then the case dimensions. As ammolab already posted, and is written in the Fulton article, the military chamber is intentionally on the large size to preclude problems a overly tight chamber might have.



Sorry
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Old October 07, 2014, 17:37   #126
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Wiki shows a few thousands of an inch variation and they are "Different sizes"?

European 6.5x55 and US 6.5x55 vary by far more and yet they are the "same"!

I better cut and paste that WIKI info to all the major Die Mfgs as we have never had 7.62NATO Die Sets available....

Interesting in the Fulton article that Clint Smith gives a headspace setting that is "perfect for both cartridges". For two different size cartridges?....Nah!
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Old October 07, 2014, 19:42   #127
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Don't fall for it Lastchip,,,,
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Old October 07, 2014, 20:10   #128
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I guess my Coonan receiver, marked .308, is junk. Bummer.
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Old October 07, 2014, 22:24   #129
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No,,,you just can't choot 7.62x51 in it.
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Old October 07, 2014, 22:56   #130
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Prolly shouldn't confuse the .308/7.62x51mm purists with the concept of P.O. Acley improved rounds.
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Old October 13, 2014, 19:35   #131
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Quote:
Originally Posted by brunop View Post
Lastchip -

our own Uncle Buck, an engineer who was employed (iirc) by Uncle Sam in small arms/ordnance has written exhaustively here. You, too, can use the Search function. It comes down to the fact that the units "PSI", and "CUP" are not even close to comparable, and the 50,000PSI vs. the 62,000 CUP (or vice versa) are not even measuring the same things. Here's an important thought exercise:

Edit to add: I see that Uncle Buck is up above in post 109 (among others) pointing out the pressure gauge standards and other things.
Uncle Buck is not an engineer. I have a PhD in science and (among other things) I have measured pressures as a Professor at the University of California for a living for the last 30 years. I teach about pressure measurements too.
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