308 vs 7.62 Nato

Discussion in 'The Ammo & Reloading Forum' started by WILD CAT, Jul 29, 2009.

  1. Bindernut

    Bindernut Well-Known Member

    Oct 24, 2007
    ND, USA
    I tend to think the same way that Popgunner says in his post...Not all 7.62x51 is loaded to NATO spec. If it says NATO, then it should pressure out to the NATO limit...but I'd be cautious with some of the oddball country of origin ammo.

    Alpo's mention of some hot PMC "NATO" stuff makes me think of pretty much every box of PMC I ever bought. I never had a rifle to run any of their 7.62 through but I have bought PMC in several other calibers. Every one of em had either really lousy brass or they were really hot...or both. In one instance, I bought a bunch of PMC 6.5Swede because that's all I could get at the time...I fired about 20rounds through a very clean & tight M96 that would handle Norma or W-W just fine. With every round I got more nervous that the rifle was about to come apart. Several cases had near head separations and the primers were very flat. I quit using that stuff and pulled them apart to salvage the brass & bullet and junked the powder charge they were using. I also scrounged harder for W-W stuff again. The PMC brass didn't last worth a hill of beans either, even with mild handloads they only lasted for 3 or 4 loadings.
    So I'm not sure if you can blame PMC for running higher than normal pressure or if they just had cheap brass. Either one could've caused the sticky bolt problems he experienced with his 7.62 NATO ammo.
  2. gdmoody

    gdmoody Moderator Supporting Member

    Sep 7, 2007
    Athens, Georgia
    After reading the posts here and LD's post about his new PTR-91 in the Large Bore/Small Bore Rifle/Shotgun forum, I now understand the problem with the 7.62 vs 308 ammo that I mentioned earlier. It was not the ammo's pressure it was the "gunk" used to seal the bullet that was breaking the extractor. Thanks guys!!


    WILD CAT New Member

    Jul 29, 2009
    Caracas, Venezuela
    GDMOODY, as far as I know, the Gunk or sealer of the bullet does not make contact with the extractor, so how does it effect the extractor. I have a K98 Mauser that I treasure and most of the rounds I intend to use now conme with some kind sealer of the bullet. Could You please give me some more information?
  4. JLA

    JLA Well-Known Member

    Feb 26, 2007
    Heart Of Texas
    If you fire a .308 buy either .308 commercial ammo (i.e. remington, hornady, federal, winchester, etc...) or look for the crosshairs stamped on the headstamp of '7.62X51 NATO' dont buy NATO ammo if you cannot first verifly that it is indeed NATO spec, and ALL NATO spec ammo bears crimped primers and the crosshair stamped in the headstamp... FYI, some of that foreign mfg. ammo was intended for machine gun use, or so I read. That explains why its much hotter than it should be...
  5. I own and shoot two Spanish built mausers. (1916 Short rifle) chambered for 7.62x51mm, One was modified by the Spanish into the FR-7 configuration. I download the NATO ammo (mfg. in South Africa) by removing 5 grains of the milsurp powder and replacing the bullet with a 123 grain Sierra. I do NOT shoot .308 Winchester or NATO ammo as issued. Since these rifles were designed around the 7x57 mm mauser cartridge which has a much lower chamber pressure than the .308 Winchester and the NATO round, the rifles are almost 100 years old, they have a two lug bolt system and the recievers are made of softer steel than are the FN and German made rifles, and primarily because I have a severe allergy to death and pain. A word to the wise, these rifles were "rode hard and put away wet" by the Spanish military, and are being sold mostly by unscrupulous dealers. CAVEAT EMPTOR!!!!
  6. gdmoody

    gdmoody Moderator Supporting Member

    Sep 7, 2007
    Athens, Georgia
    It does not touch the extractor, but reading the other thread I mentioned, I can see that the gunk sticks the case in the chamber and makes it very difficult to extract the case which is "cemented" to the chamber. This, as I see it, could either pull the head off the case or jerk the extractor out of the bolt, which is what I think was happening.

    WILD CAT New Member

    Jul 29, 2009
    Caracas, Venezuela
    From the comprehensive posts on this thread I find difficult to choose an answer. I think it would be an expensive error to unwillingly shooting anything but factory rounds and turn out shooting a clone destroying the gun. Any way thank You all.
  8. GMFWoodchuck

    GMFWoodchuck New Member

    Oct 9, 2008
    Binghamton, NY
    In a modern .308 rifle it will be safe to shoot all 308 and 7.62 ammo of reputable manufacture. Meaning if it has a federal, winchester, or some other company that you know to be a good company the ammo will be safe. If the ammo is being sold by bass pro shops, midway, or some other company it will also likely be safe. If you go to a random gun show and see a table that has 7.62 ammo from a company that you have never heard of walk away. Besides any new rifle sold in this country with the 308/7.62X51 dimensions will likely be marked 308 anyway. If you chose to buy an older military rifle marked with the 7.62 destination use the NATO marked 7.62 ammo. However, if you come across a used bolt action sniper rifle that's branded 7.62 you should also be safe being that any you would come across are going to be the exact same gun (Rem 700, savage 110, Win 70, and etc) as the cilivian version mechanically speaking. The only practical difference will be in how they look.

    In short, if you're going new, you almost do not have much choice but to buy a 308 rifle. If you're going used, the only 7.62 branded guns will be of military type and you should be using NATO marked ammo for all the reasons the others have already said. Older civilian guns will likely be 308.

    In either case with 7.62 ammo or any ammo for any gun, if you're not sure if it's any good. Do not buy it.

    Do not worry. Which ever destination you chose there is plenty of safe ammo of reputable manufacture. If you want to hunt you might be a bit better off with a 308 being that there is way...way more hunting ammo with the 308 destination versus the 7.62. Most 7.62 ammo, from I see, is typical target type.
    Last edited: Aug 25, 2009
  9. Hammerslagger

    Hammerslagger New Member

    Jul 30, 2009
    I was reading this thread and "scratching my head" in disbelief relative to 308 Win. pressures increasing from 52K to 62K range in recent years under SAAMI guidelines. Especially, since SAAMI seems to have reduced pressures (and thus performance) for almost everything over the last 50 years.

    It has long been known that PSI values obtained by Piezo Transducers are not exactly the same pressure values obtained using the older copper or lead crusher cylinder method. However, few (including myself) realize that these values can vary from 52K to 62K depending only on the measuring method used.

    For those with serious academic interest, go to: http://kwk.us/pressures.html
  10. 29yrhkr

    29yrhkr New Member

    Sep 10, 2009
  11. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    The reference to my PTR-91 problem:

    According PTR INC. (PTR-91 manufacuturer):

    TAR LIKE SEALANT used in:
    South African
    Winchester white boxes marked 7.62
    Venezuela Cavim
    Austrian Hirtenberger
    Some lots of German

    In the PTR and H&K 91 variants the chamber is fluted to allow easy extraction of the cases against the roller lock action of these guns. In WWII and after, when the guns were developed originally, this fluting solved the hard extraction problem. The idea was that some of the gas pressure in the flutes of the chamber works against that in the case to minimize the hold the chamber has on the brass case. It normally works fine but the tar sealant goes into the flutes and coats the chamber wall making the chamber eventually stick to the cases, locking up the gun.

    Would this happen in a bolt gun? I am not sure but it seems to me the pressure would expand the cases tightly against the chamber wall, locking out all the gasses from getting to the chamber wall at least initially. If the gun shows excessive blowback of the gases on the body of the outside of the case then the cases MAY get stuck to the chamber wall. But I don't think that would happen normally. It is my opinion that the tar sealnt would not effect the extraction of the cases from a bolt gun but indeed causes problem with extraction from the H&K 91 and its clones. We proved it through the use of South African ammo in a brand new PTR-91. Cleaning the chamber and changing to reloads eliminated the problem completely.

    Broken extractors are usually associated with hard extraction often caused by excessive headspace (it says here ???). Or can be caused by rough chamber walls from corrosion from corrosively primed ammo usage in the life cycle of the gun. Smoothing the chamber with a drill motor and a stick wrapped in very fine sand paper, like 600 grit, often solves the problem IF you don't remove too much metal from the chamber walls to get the rust out. A smooth chamber aids extraction. Oiling the ammo cases can too but that makes the bolt work harder as the case friction is lost and the bolt has to take the full brunt of the pressure.

    Finding the cause of extractor breakage is a process of eliminating the things correct with the gun only to end up with only the problem left.

    Last edited: Sep 11, 2009
  12. Joker18

    Joker18 New Member

    Oct 22, 2009
    Southeastern US
    The big and major difference between 7.62X51mm NATO ammo and the .308 Win is the throat dimensions of the NATO 7.62 X 51 chambers are different and if my old memory serves me well the NATO chamber throats are deeper. Most current Milsurp ammo in 7.62X51 is loaded for military gas operated rifles and should be fine with any commercial bolt rifle chambered for .308 Win. The only exception is some of the 7.62 Indian surplus produced for belt fed machine guns that has been de-linked and sold as loose ammo. Some lots of that ammo was quite hot and are not recommended for M1A's and other gas operated military rifles.
  13. Vael

    Vael New Member

    Aug 14, 2010

    308 Max Pressure - 62k PSI
    7.62 NATO Max Pressure - 50k CUP ... or 60-61k PSI.


    7.62 NATO brass is THICKER than 308 brass. Since they have nearly the same exterior dimensions and 7.62 brass is thicker, the levels are reduced by about 2 grains.

    If you really want to know the difference between 7.62 NATO and 308, I would suggest reading this:
    http://home.comcast.net/~ehorton/The Truth About 308 Win and 762 NATO.pdf

    Edit: For a short answer to if you can use 308 or 7.62nato in a rifle. I would say if you have a good quality rifle and good quality ammo, either should work fine. The main problems come mainly from severe out of spec exterior dimensions, not pressure. So if you have a tight tolerance, precise 308 rifle and you try to use some crap 7.62 from a 3rd world country, it might not work so well.
    Last edited: Aug 14, 2010
  14. Vael

    Vael New Member

    Aug 14, 2010

    Ok, from my limited experience, I've noticed that most 308 companies download further away from their max compared to the military. For example, the 308 round at 62k psi max usually only gets loaded at 55k psi. The 7.62x51 nato round with a 60+k psi max will often get loaded to 58-60k psi. I think this is mainly to do with the 7.62 using thicker brass and being able to handle its max psi much better. So really, if you have a weak extractor and are running military 7.62, it might be too hot for your gun.

    See above post for more information.
    Last edited: Aug 14, 2010
  15. Popgunner

    Popgunner Active Member

    Dec 3, 2005
    This is the link I posted here on TFF on loading blank cartridges where the guy stated 7.62 NATO cases are thinner than commercial cases. This may or may not be true in some types of NATO cases.

    This article has been done away with for unknown reasons.

    vael: you seem to be setting yourself up as an expert in this area. Making statements such as:

    "Ok, from my limited experience, I've noticed that most 308 companies download further away from their max compared to the military. For example, the 308 round at 62k psi max usually only gets loaded at 55k psi. The 7.62x51 nato round with a 60+k psi max will often get loaded to 58-60k psi. "

    Was this limited experience you had that caused you to notice this phenomenon with any type of testing equipment? Maybe you just surfed the net & took as gospel what you saw written?

    You & FAL Phill that wrote your article seem to think exactly the same. Are you two one in the same? FAL Phill seems to be arguing these points with many knowlegable folks on several gun forums.

    The M-118 match load you use to say NATO ammo is in the 61k psi range is not regular 7.62 NATO ammo.

    I'm just sayin':)
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