Okay, I have heard people say yes and no. I'm thinking of getting a FAL, CETME or SOCOM next year (depends on the overtime available when I purchase) and I was wondering if it's ok to shoot .308 (probably Bear) in a 7.62x51mm chamber. What is the chamber pressure difference?
Is it ok to shoot .308 in a rifle chambered for 7.62x51mm?
- Thread starter Patriotme
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Ben Shepherd
Member
Commercial 308 is loaded hotter than NATO spec 7.62X51. Even if official cmaber specs are "looser' tolerance wise. Generally it's not a good idea to do so.
svaz
Member
What Ben said. .308 is too hot for a x51 rifle. Check out the specs on each cartridge (PSI).
mljdeckard
Member
I shot some .308 in my M1A. I started getting failures to eject when it got hot.
The military spec is in cup, the SAAMI spec in psi taken with a piezo-electric gauge.
Any quality rifle chambered for 7.62 NATO should accept and fire .308 Winchester safely. Note that this statement does NOT apply to some old rifles originally made for 7x57 and altered to use 7.62 NATO or cartridges dimensionally identical but of lower power.
Jim
Any quality rifle chambered for 7.62 NATO should accept and fire .308 Winchester safely. Note that this statement does NOT apply to some old rifles originally made for 7x57 and altered to use 7.62 NATO or cartridges dimensionally identical but of lower power.
Jim
BHP FAN
Member
Right, but then you just down-load. Always taylor your ammo to the rifle.
Seems to me I heard and have documentation in the reloading room down in the dungeon and I was told if it is stamped on the barrel 7.62x51 a person should shy away using commerical .308..Difference is military brass is thicker while regular 308 is thinner, this results in the amount of propellent used in both rounds. I have a DMPS LR 308 Panther which the barrel is stamped "308" and I don't have any problem using either or.. I would go downstairs and retrieve the info but cannot climb stairs yet due to a recent hip replacement.. Anyways I hope this helps you out.
BHP FAN
Member
You got it right in one, no need to risk further damage to your hip. You can always start with a 10% reduced load,and work your way up. Check out Richard Lee's ''Modern Reloading'',though. Some powders can detonate with reduced loads, due to ''flashover''.
Thanks for the info. I thought that I had read that commercial .308 was not to be used in 7.62's but I just read an article in The Blue Press by Jerry Ahern (Ahern Under The Gun: How To Feel Fine When It's TEOTWAWKI) and he recommended having .308's. He then went on to talk about CETME's and mentioned .308 instead of 7.62x51mm.
What a shame. I was considering a CETME and would probably buy mostly Bear in .308. If I'm stuck purchasing nothing but 7.62 I might look around a bit more.
What a shame. I was considering a CETME and would probably buy mostly Bear in .308. If I'm stuck purchasing nothing but 7.62 I might look around a bit more.
USSR
Member
+1. Another exception is a M1 Garand converted to 7.62x51. Not because of peak pressure concerns, but because of possible op rod damage due to high port pressure.
Don
Hundreds (if not thousands) of military rifle competitors have used commercial .308 Win. ammo in their M1 and M14 rifles chambered for the 7.62 NATO. No problems whatsoever. And the same number of civilians have used 7.62 NATO ammo in the commercially chambered bolt action match rifles; again, without problems.
There's as much difference in chamber specs between the two rounds as their is between commercial and arsenal ammo dimensions.
If there really was a "safety" problem, how many readers think a warning about it would be printed on each box of ammo of either type? And are there any safety issues in print packaged with new commercial .308 Win. rifles?
And the high port pressure issue with converted Garands is a myth. When Springfield Armory in MA chambered Garand barrels in the early 1960's made with 1:12 twists (they used single-pass broach riflers that also made M14 barrels) for the USN and USAF, the gas port hole was the same size as the 30 caliber barrels used. People in the service shops converting 30 caliber M1's by rebarreling them soon learned the port pressure wasn't high enough. The op rod didn't push the bolt back far enough for complete and proper cycling. So they drilled out the gas port hole several thousandths on all those 7.62 NATO chambered Garand barrels so they did all the right stuff. I've watched the armorers at the Navy Match Conditioning Unit take a new 7.62 Garand barrel out of its box, drill out the gas port then knurl the lower band area so to get a super tight fit of the band to the barrel when it was pressed on and pinned in place.
If one digs around and finds the chamber specs for military 30 caliber and 7.62 NATO rounds, they'll see they were both 50,000 CUP. 50,000 copper units of pressure is the same as 57,898 pounds per square inch, but it's not a linear scale. They're equal at 34,693.80. Confusing as all get out, but such is life in the world of measurement standards. Even the meter's official exact length has changed a few times since it was originally defined as one ten-millionth of the length of the meridian through Paris from pole to the equator.
There's as much difference in chamber specs between the two rounds as their is between commercial and arsenal ammo dimensions.
If there really was a "safety" problem, how many readers think a warning about it would be printed on each box of ammo of either type? And are there any safety issues in print packaged with new commercial .308 Win. rifles?
And the high port pressure issue with converted Garands is a myth. When Springfield Armory in MA chambered Garand barrels in the early 1960's made with 1:12 twists (they used single-pass broach riflers that also made M14 barrels) for the USN and USAF, the gas port hole was the same size as the 30 caliber barrels used. People in the service shops converting 30 caliber M1's by rebarreling them soon learned the port pressure wasn't high enough. The op rod didn't push the bolt back far enough for complete and proper cycling. So they drilled out the gas port hole several thousandths on all those 7.62 NATO chambered Garand barrels so they did all the right stuff. I've watched the armorers at the Navy Match Conditioning Unit take a new 7.62 Garand barrel out of its box, drill out the gas port then knurl the lower band area so to get a super tight fit of the band to the barrel when it was pressed on and pinned in place.
If one digs around and finds the chamber specs for military 30 caliber and 7.62 NATO rounds, they'll see they were both 50,000 CUP. 50,000 copper units of pressure is the same as 57,898 pounds per square inch, but it's not a linear scale. They're equal at 34,693.80. Confusing as all get out, but such is life in the world of measurement standards. Even the meter's official exact length has changed a few times since it was originally defined as one ten-millionth of the length of the meridian through Paris from pole to the equator.
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Could you elaborate on that please?
I was under the impression that there was a slight difference in chamber specs, but not in external ammo dimensions. If there was a difference in external dimensions of hte cartridge, would you not need a different set of dies to load 7.62 NATO? Reloaders use the same dies for both.
USSR
Member
Not so, Bart. You cannot use slow burn rate powders in a Garand, whether in .30-06 or .308, without possibly battering the back of the receiver and/or bending the op rod. There is commercial .308 ammo made that uses suitable 4895 burn rate powders, but unless you know that they are using a suitable powder, you risk damage to your Garand. While the Garand has a very strong action, the weak link of it is the gas system, which was made to operate within a very specific pressure range. The axiom for ammo for the Garand has always been: no powder faster than IMR3031 or slower than IMR4320, and no bullet heavier than 180 grains.
Don
I thought we already did this one this month. http://www.thehighroad.org/showthread.php?t=486432
jonnyc
Member
Just about everything posted above Bart is crap. Commercial .308 and 7.62x51 are the same round...period. There are commercial .308s loaded hotter AND lighter than Nato-spec 7.62 ammo, and not all 7.62x51 rounds are loaded to the same specs. The only difference between them is the internal construction of the case head. Military brass has a thicker web to withstand MG extraction, and the flutted chamber extraction of Cetme-type rifles. If you don't reload the "two-named" rounds are interchangeable. If you reload, you must take into consideration that the internal capacity of a military case is a bit less that that of a commercial .308 case.
Jim Watson
Member
Military chambers are a bit roomy by commercial standards.
Nothing mysterious, they are meant to be shot fast, hot, and dirty, with ammo of doubtful origin, the NATO cross notwithstanding. Nobody picking up empties out of your foxhole to reload, either.
Nothing mysterious, they are meant to be shot fast, hot, and dirty, with ammo of doubtful origin, the NATO cross notwithstanding. Nobody picking up empties out of your foxhole to reload, either.
USSR (Don) sez:
The USN and USAF rifle teams used 44 grains of IMR4320 under a Sierra 190 in primed M118 LC match cases with great accuracy in long range matches.....and a substancial "ping" when the op rod and bolt struck the rear limits then rebounded robustly until the bolt locked open.
More than a few Garand shooting civilian folks took their bent op rodded M1's to the USN/USAF van for work on them 'cause they stuffed .30-06 cases full of IMR4350 or 4831 under 200 grain bullets like the bolt gun folks used. I was standing near the van one afternoon when a civilian was told the load he quoted as safe in his bolt gun was the cause of his M1 rifle's demise. He cussed the armorer and told him he was stupid 'cause it was a mild load and his Winchester took it just fine. .........such is life.
I agree that the Garand has a narrow range of acceptable port pressure for either round. I was referring to a straight conversion from .30-06 to .308 with the same gas port diameter and ammo with the same 50K CUP pressure numbers. With a 10% lower powder charge and an extra half inch of bullet travel from case to gas port, there will be lower pressure at that point. Another reason why 7.62 NATO M1's have lower muzzle velocity for the same peak pressure and bullet than a .30-06 one does with the same length barrel. Which is why the arsenal 7.62 M1 barrels had to have their gas port opened up a bit.
The USN and USAF rifle teams used 44 grains of IMR4320 under a Sierra 190 in primed M118 LC match cases with great accuracy in long range matches.....and a substancial "ping" when the op rod and bolt struck the rear limits then rebounded robustly until the bolt locked open.
More than a few Garand shooting civilian folks took their bent op rodded M1's to the USN/USAF van for work on them 'cause they stuffed .30-06 cases full of IMR4350 or 4831 under 200 grain bullets like the bolt gun folks used. I was standing near the van one afternoon when a civilian was told the load he quoted as safe in his bolt gun was the cause of his M1 rifle's demise. He cussed the armorer and told him he was stupid 'cause it was a mild load and his Winchester took it just fine. .........such is life.
Uncle Mike
Member
It's OK...!
Ben Shepherd
Member
Um, no.
Bold emphasis mine, full article- http://www.6mmbr.com/308Win.html Scroll all most to the bottom of the page.
So while it's true that the problem lies mostly with the earlier rifles converted from the Mauser round, the is most certainly a difference, and it is to be respected and understood should one want to keep both his rifle and his person whole(worst case scenario, but a distinct possibility). While it's true there are lower pressure loadings in 308 like the "reduced recoil" offerings from Federal and Remington, on the whole, commercial 308 is loaded hotter than the majority of surplus 7.62X51. Will you experience a catastrophic failure? Most likely not. But it's still something of which one should be aware.
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Grease Monkey
Member
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I understand the pressure issue, but are the white box or brown bear rounds you buy loaded that high?
W L Johnson
Member
From Armalite if you have an AR-10
Actully not so full of crap. The main issue is the case. Try to run 1000 rounds of .308 tru a M-60 and get back to me. The thiner .308 stuff will shorten up as the bolt slams it in and blow the head off the case. As loads and such yes in bolts and semis auto guns the .308 and 7.62 will be no issue mixing up....belt feed guns forget it unless you like singed eyebrows. You guys are missing the main point...7.62 has a heavy case so it will feed in belt fed MGs...308 dont...
jonnyc
Member
To Ben and Buttrap,
Um...yes it is. Those "SAAMI" and headspacing issues have been dealt with before by others much smarter than me. And if you read my complete post, you'll see I did deal with the MG issue.
And this: "commercial 308 is loaded hotter than the majority of surplus 7.62X51". You can't honestly be making such a broad and incorrect statement with a straight face.
Um...yes it is. Those "SAAMI" and headspacing issues have been dealt with before by others much smarter than me. And if you read my complete post, you'll see I did deal with the MG issue.
And this: "commercial 308 is loaded hotter than the majority of surplus 7.62X51". You can't honestly be making such a broad and incorrect statement with a straight face.
Bill_Rights
Member
Patriotme,
I agree along the lines of what W L Johnson said: Get a rifle that can handle the full range of .308Win (huge range of loadings) and 7.62x51mm NATO (only two loadings I know of, the 147 grain standard round and the sniper round at 185 gr.).
Among the rifles well-reputed to handle the full range is the FNAR from FNH USA. You might consider it for other reasons, as well.
P.S. - I am not an old-timer on this forum, but I might as well be the one to jump up on the "holier than thou" soapbox first: This issue of 7.62x51mm NATO versus .308Win has been handled excellently in numerous threads on this forum, even since I joined and well before that, too. Use the SEARCH function creatively. THE MAIN POINT IS: GET A RIFLE THAT HANDLES BOTH/ALL - since you haven't bought yet, you have that luxury.
I agree along the lines of what W L Johnson said: Get a rifle that can handle the full range of .308Win (huge range of loadings) and 7.62x51mm NATO (only two loadings I know of, the 147 grain standard round and the sniper round at 185 gr.).
Among the rifles well-reputed to handle the full range is the FNAR from FNH USA. You might consider it for other reasons, as well.
P.S. - I am not an old-timer on this forum, but I might as well be the one to jump up on the "holier than thou" soapbox first: This issue of 7.62x51mm NATO versus .308Win has been handled excellently in numerous threads on this forum, even since I joined and well before that, too. Use the SEARCH function creatively. THE MAIN POINT IS: GET A RIFLE THAT HANDLES BOTH/ALL - since you haven't bought yet, you have that luxury.
Its not a head space issue or chamber pressure at all..its the thinner .308 case not liking getting hammered in a belt fed gun by that heavy bolt. They do and will get about a 1/2 inch shorter and blow the case heads off. You can debate head spacing and chamber pressure till the hogs come home but that thinner 308 case is a lot diff than a 7.62 when a huge bolt slams it to heck and hell.
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