7.62 NATO or .308 win

Discussion in 'General Firearm Discussion' started by Lonnie68, Mar 7, 2010.

  1. Lonnie68

    Lonnie68 New Member

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    I am getting ready to order a LR-308C. My issue is the ammo,it is listed in a 7.62x51 heading and not with the .308 listings anymore.Is the .308 win round acceptable to shoot in that rifle or should I stick to the 7.62 NATO? I have read and been told that they are the same,others argue that they are close but not the same round.I do not want to damage the rifle, neither immediately or later on.I have been doing some research but can't seem to get any definite answers one way or the other.It is a pretty large investment to damage.I have sent an email to the manufacturer but haven't gotten a response yet.I reload my own ammo and looked through my books,one doesn't list the 7.62 NATO,and another lists it with the .308 win.Any input would be GREATLY appreciated.Thanks.
  2. landcbeitner

    landcbeitner Member

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    I beleive that 7.62 NATO has a lower opperating pressure than 308win and that's the only significant difference. Since you re-load just don't load max pressure 308 loads and you'll be fine. You may find some factory 308 hunting ammo is fairly high pressure and shouldn't be used in your rifle.
  3. onearmedswordsman

    onearmedswordsman Member

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    Lonnie,
    I don't own a LR308, but have considered getting one for some time. That's why I know what I am going to share with you.

    About two years ago, DPMS explcitly indicated it was chambered to 308 win rifle. Then, information abrutly changedto 7.62 NATO.

    In my mind, the problem is 308 win pressures (55,000 PSI max) are not only higher than 7.62 NATO (50,000 PSI max), but some of us who handload for 308 win bolts wish pressures beyond data because most modern bolt rifles can handle it. DMPS has gone as far as voiding the warranty if you handload. The result of living in a litigious society.

    As for 7.62 NATO service rifle load data, Hornady's 7th edition, page 451 has data for their 155, 168 and 178gr A-Max and HPBT bullets.

    If you handload, I say handload using "service rifle" data. You have to handload to get the accuracy worth calling home about, make that trip to the range worthwhile.

    Check this, too. Search for "M118":
    http://generalcartridge.net/Documents/TM43-0001-27.pdf
  4. Scott

    Scott Well-Known Member

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    DPMS will tell only shoot .308 in your chambered .308 barrel and you can shoot 7.62 and .308 out of a 7.62 barrel.

    From DPMS:
    Subject: Can I use 7.62x51mm ammo in my .308?
    While you can physically fire either 308 or 7.62 NATO from a 308, you
    will see reduced accuracy from increased wear in the throat of the
    rifling and a higher chance of erratic cycling, including a higher
    chance of failures to extract. It is for this reason we recommend using
    only commercial 308 in a 308 barrel.

    DPMS does not recommend or warranty the use of 7.62x51 ammo in a .308 chamber.

    A 7.62x51 chamber can handle both types of ammo. Determine your actual chambering by looking on the underside of your barrel forward of the gas block or front sight base.

    The lower receivers of these two rifles are identical and will be stamped 308 even on a 7.62, the lower stamp should not be used to determine actual chambering. FWIW, the .260, .243, .300 SAUM, .308, 7.62x51 and 6.5 Creedmoor all use the same lower receiver.
  5. onearmedswordsman

    onearmedswordsman Member

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    308win vs 7.62 NATO is the opposite to 5.56 NATO vs .223 REM. 308 win max pressure is 5kpsi higher than 7.62 NATO. DPMS response is counter intuitive. But they are the manufacturer, and if that is what they say, then, I but1 out.

    Lonnie, if DPMS ever responds, please, post.
  6. Lonnie68

    Lonnie68 New Member

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    Thanks for all of the input guys,I will definitely post the reply from DPMS.
  7. Buddhalux

    Buddhalux Active Member

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    If they're like the 5.56/223 rounds then the bullet throating is going to be longer on the 7.62 rd.
  8. coosbaycreep

    coosbaycreep Bronze Supporter Bronze Supporter

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    I've always read that aside from lower pressures, 7.62 is also suppose to have thicker brass than commercial .308, which is why a lot of people recommend only shooting 7.62 in some of the weaker .308s like Ishapore enfields, or in guns that are rough on brass.
  9. onearmedswordsman

    onearmedswordsman Member

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    Ishapore Enfields are 7.62 NATO, not 308Win.:cool:
  10. HahnsXD

    HahnsXD Active Member

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    Yeah, I was told only to use 7.62x51 in my old CETME becuase they have a nasty habit of tearing .308 brass in half...
  11. JumpWing

    JumpWing Member

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    5.56 is a little more potent than .223
    .308 is a little more potent than 7.62 NATO

    DPMS is basing their advice on the general idea that it's bad to use a round other than what the weapon has been chambered for. There's nothing inherently wrong with that advice; your weapon will be more accurate and probably last longer by using the recommended cartridge.
  12. Lonnie68

    Lonnie68 New Member

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    According to Jon Fritz at DPMS,the LR-308C has the 7.62x51mm chamber and can shoot either round without issue.So,now we know.Thanks for all of the input folks.:thumbup:
  13. usmc

    usmc Active Member

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    Before we go much further, we want to address the oft-posed question "Are the .308 Winchester and 7.62x51 NATO one and the same?" The simple answer is no. There are differences in chamber specs and maximum pressures. The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62x51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win "Go Gauge" is 1.630" vs. 1.635" for the 7.62x51. The .308's "No-Go" dimension is 1.634" vs. 1.6405" for a 7.62x51 "No Go" gauge. That said, it is normally fine to shoot quality 7.62x51 NATO ammo in a gun chambered for the .308 Winchester (though not all NATO ammo is identical). Clint McKee of Fulton Armory notes: "[N]obody makes 7.62mm (NATO) ammo that isn't to the .308 'headspace' dimension spec. So 7.62mm ammo fits nicely into .308 chambers, as a rule." You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62x51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max.
  14. tac

    tac Active Member

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    That is correct.

    The internal dimensions of the base of the NATO cartridge case are substantially more beefed up by comparison with the commercial case. This is because the original cartridge was designed from the onset to be reliable in fast-firing semi-autos and fully automatic military weapons. Bear in mind that at the time of introduction in the late 1950's, the US did not employ a particularly fast-firing fully auto machine gun like the MG3/42/58 used by so many of its other NATO partners. This gun, originally the German MG42, fires at around 1100 rpm, uses a disintegrating link feed, and as a result the mechanical forces acting on the case, particulalry in extraction, are fearsomely prodigious.

    So the internal case capacity of the .308Win is greater than the 7.62 case as a result. This equals greater powder capacity, and the resulting higher pressures with higher velocity.

    Typical differences in case volume are as much as 5-7%, dependant on manufacturer.

    tac - shooter of both calibres
  15. 45_70Sharps

    45_70Sharps Member

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    That's what I thought also. A little checking shows some case differences. 7.62 is built stouter. They are very close to the same, but not quite the same size.

    Attached Files:

  16. powermad

    powermad Active Member

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    Those are not case dimensions they are chamber dimensions.
    Military style weapons can handle excessive headspace as long as 7.62NATO is used
    W.E.G. at the falfiles posted his results a bit ago on cartrige headspace.
    [​IMG]

    Pressures.. one scale is military, the other civilian.
    Completely different and not convertible. In the end they are nearly the same for the same type of round, 147-150 grains.

    Headspace is where you need to be concerned about in a military style 7.62x51 mm rifle and shooting commercial ammo.
    Granted no hot rod loads, improper loads need to be explained.
    Keep the bullet to 168 gr loads and it should be fine.

    I set the HS on a FAL at 1.632. FN minimum specs.
    If I ever manage to be able to close a 1.634 no-go on it in my life time I will be amazed.

    Food for thought.
    Belgian civilians were not able to own rigs with military ammo markings.
    FN changed the lettering from 7.62 to .308 match and walla.
    Belgian Joe can now buy the same FAL as the military.
    Other than a stamp FN made no changes to the rifle.

    I feed mine a regular diet of federal 150 gr soft points.
    My 2 cents.

    If the gun sux.. oh well
  17. Gunner3456

    Gunner3456 Well-Known Member

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    It's been mentioned already that the 7.62 brass is thicker than .308 and therefore has less interior volume in the case.

    With less case volume but the same primer and the same powder charge, pressure will build faster and higher in the 7.62 brass than in the .308 brass. If buying mil surp brass in 7.62 to reload as .308, it's important to know this and to reduce the powder charge slightly. This is where a chrony is ever so handy because we can't actually measure the pressure. We can get some reasonable information from bullet speed though, since it's all we have. We can start about 10% low on the charge per .308 specs when using 7.62 brass, and work up if needed.

    For liability purposes I hesitate to offer actual recipes, but they are all over the net via google.

    Just for me, to get .308, I'm comfortable using mil surp brass, starting 10% low on powder charge, and then working up until I get the bullet speed the same as factory .308.

    However, please ask the powder manufacturer and don't take my word for it. What I've been told and what works for me may not be safe for your rifle.

    Just be aware that the powder manufacturer's load data for .308 will spike higher in 7.62 brass and could cause real danger in some guns, so make proper adjustments for it.

    $.02
  18. BulkAmmo

    BulkAmmo New Member

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    Hey Lonnie, it sounds like you got some good info deciding between the civilian and NATO round but since the issue comes up a lot I thought this might help on the whole differences between .308 and 7.62x51 topic:
    BA_Infograph.png
  19. Quacky88

    Quacky88 Active Member

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    Wow very educational thread thanks all.