.308 Winchester & 7.62x51mm NATO?

Discussion in 'Firearms' started by Sharpie44, Jul 7, 2009.

  1. Sharpie44

    Sharpie44 Monkey++

    Ok I just traded for a Hesse arms G3. (I know I know it’s Hesse but I took a gamble.) I got twelve steel mags and two aluminum along with 300 rounds of ammo and some furniture for the gun.

    After getting It all home I realized that about 60 rounds of the ammo is not 7.62x51mm NATO it’s .308 Winchester. I looked online and as usual opinions are all over the place as to whether or not it’s a good idea to use .308 Winchester in a 7.62x51mm(.308 NATO) gun. I don’t have a .308 winchester so I’ll have to sell/trade the ammo if I can’t use it. With the ammo shortage I would hate to have to lose the 60 rounds.
  2. tacmotusn

    tacmotusn RIP 1/13/21

    Well, I was never aware until just a few years ago that there was a difference. I guess it is the exact placement of the shoulder and angles that is the difference as i understand it. My DCM garand was 7.62 x 51 at my request. I was familiar with prior 30-06 garands issued to the US Navy 1967-70 in that chambering. I fired both military 7.62 x 51 and commercial .308 Win. thru it with no problems. I had a bolt action Remington in .308 win at the same time and also ran my reloads in .308 win thru both. All the once fired military 7.62 had to be full length sized to .308 win to work properly in the bolt gun .... I don't know if I could have skipped full length sizing and used it in the garand or not. I have always had all guns of mine in .308 win or 7.63 x 51 digest new ammo interchangably of either ilk. It seems to me the problem might be fire formed brass in military chambers have larger dimensions overall than fire formed brass in most civilian .308 win chambers. I full length size them each and every time because I have 3 different .308 win chambered guns and want no problems.....so far reloads work every bit as good as new loads. All the above JMHO of course.
  3. Minuteman

    Minuteman Chaplain Moderator Founding Member

    I had to do a little checking on it. I have always used them both with no problems.
    But it seems that there is a lot of internet discussion on the subject. But as a rule it appears that the oft repeated case length and pressure differences are more hype and faulty interpretation of the data.

    Below is a sampling of some of the discussions and the consensus seems to be that, yes there is a difference. But no it doesn't matter.

    This is from Fulton Armory

    They are not the same, 'cause the .308 Win was released by Winchester several years before the Army standarized the T64E3 as the 7.62MM. You'll get an endless discussion of pressure specs, endless because SAAMI and the Ordnance Dep't measured pressure in different, unrelateable ways. Howver, the chamber drawings are different.

    They are the same, 'cause nobody (and Clint's been looking for many years!) makes 7.62MM ammo that isn't to the .308 "headspace" dimension spec. So 7.62MM ammo fits nicely into .308 chambers, as a rule.
    But in some 7.62MM rifles the chambers are long (to the 7.62MM military spec), notably the Navy Garands with 7.62MM barrels. Thus, using commercial ammo in such a rifle is not a good idea; you need stronger brass.

    This is a summary of the discussions

    They are infact, "the same", with a few foot-notes.

    People confuse themself over the "pressure". Sometimes they don't get there is a difference between CUP and PSI, however, also that NATO and SAAMI read pressures at different locations. Given the pressure curve of the burning/expanding powder, of course the two readings will be different (different locations in the barrel).

    The next issue over headspace gauges - military chambers tend to be oversized. Fact of life. 308 WIN and 7.62x51 both have the same EXTERNAL case dimensions and same cartridge overall length.

    If there was a significant difference externally, SAAMI would have it listed as an unsafe combo (they DON'T).

    Pick up Lyman #49 manual. One section - "308 Winchester (7.62x51mm NATO)". Its the same thing.

    The only SIGNIFICANT difference is the INTERNAL case dimensions. Yes, military brass tend to be thicker resulting in less internal capacity which means peak pressures may be reached with as much as 2 grains less powder than commerical brass. This is only a consideration if you're reloading. Factory loaded ammo takes this into consideration.

    The only other issue relative to the two rounds is powder burn rates. Max pressures are the same, but pressure curves are different. Gas guns like the M1A require a certain pressure at the gas port to cycle the action...commercial ammo with slower powders may have excessive pressure at the port resulting in extra wear on the action cycling.
    Lyman #49

    If your rifle/pistol is chambered for .308 Winchester it will safely shoot 7.62 Nato aka 7.62x51mm. However The .308 Winchester and 7.62x51mm cartridges are not identical and there are minor differences in their inner case dimensions, though SAAMI does not list either cartridge as unsafe in a firearm designed for use with the other.

    Yes, it will fire both. But if you're handloading, you need to be aware that military brass tends to have less case capacity than commercial brass, and your maximum load in the former will probably run a couple of grains less than in the latter.

    There's a lot of hoopla about the theoretical dimensional differences, but nobody actually makes a case for one that won't do in the other. There's also a lot made over the pressure differences, with at least one site quoting the 308 Winchester's maximum pressure as 62,000 psi vs. 50,000 for the 7.62x51, suggesting the former has a maximum pressure 12,000 psi greater than the latter. This is most decidedly not the case, either. The numbers are fine, but they measure different pressures and can't be compared in that manner.

    Of course, self-loaders can be picky about the ammunition they'll digest, but there's no reason to think the headstamp on the brass is going to make the difference, and there's certainly no reason not to shoot either in a modern bolt-action (though some of those rechambered Indian SMLE's and such make me nervous with either).





    So it seems that there is a difference but they are the same round. The only real caveat, repeated in a couple of articles is the older 7.62X51 Garands seems to be chambered slightly different and may have trouble with commercial .308. But other than that any modern rifle should fire either round safely.
  4. sniper-66

    sniper-66 Monkey+++ Moderator Emeritus Founding Member

    What Minuteman said. I'll add this. They are interchangeable, the difference as noted is that mil brass is thicker in the web so that the case can withstand the larger chamber dimensions of the machine guns. Machine guns have over sized chambers so that they can digest out of spec ammo, dirty ammo, and gunk in the chamber.
    When machine guns fire, the brass expands to try to meet the chamber dimensions and it will ruin the brass by stretching. If you try to reload mil brass fired through a machine gun, you take the chance of case head seperation. Full length resizing will typically push the brass back ino spec, but if cracked, you will seperate the head and jam your rifle. If you have new ammo, there is no problem shooting either, just if you reload, seperate and reload by batch with loads specific for that brass.
  5. Seawolf1090

    Seawolf1090 Retired Curmudgeonly IT Monkey Founding Member

    The HK and CETME paltforms have no problem with the pressure either way - it is a very forgiving system and not as temperamental as a gas-operated firearm. BUT..... the HK/CETME have a violent extraction cycle, that CAN rip a thinner commercial brass case in half. I have experienced this myself. I have fired forty .308Wins, and had one case separation.
    Be careful with the .308s, and make sure it functions properly for each shot.
  6. Minuteman

    Minuteman Chaplain Moderator Founding Member

    All the articles I found stated that reloaders are the ones who have to be careful with brass. As Sniper stated military brass is thicker cased.
    I shoot belt feds and only shoot mil-surp through them for that reason.
  7. QuietOne

    QuietOne Monkey++

    What was said before plus equal weight commercial and mil-spec will shoot to different points of aim.
  8. E.L.

    E.L. Moderator of Lead Moderator Emeritus Founding Member

    Ditto, my uncle has a H&K 91 that rips the brass on each case when ejected.
  9. Sharpie44

    Sharpie44 Monkey++

    Thanks for all the info. I'f I feel like dragging out the reloading equipment from the darkest reaches of the basement. i'll keep the inner case size in mind.

    On another note can someone tell me why the G3 is running so darn dirty. I've never owned a gun that turned my hands black and took such a long time to get spotless after only a mag and a half wroth of ammo threw it. Then again I've never owed a semi auto before.
  10. tacmotusn

    tacmotusn RIP 1/13/21

    One question before I offer an opinion on that. Do your fired cases show dark stripes in their exteriors? oh heck, why drag it out. ... H&K platforms if made under true H&K specs, do that because of the chambers being fluted to aid in not having cases stuck in chamber and having gases from firing sorta slip along side or inbetween case and chamber when firing. My sporter H&K SL-7 is a case in point. It doesn't seem to interfere with functioning reliability. You can be quite an idiot with not cleaning and put countless rounds thru it without a single jam. not that "I" would ever .... lol..... ever, do such a thing.[rofllmao]
  11. tacmotusn

    tacmotusn RIP 1/13/21

    Before I catch "crap" from "ALL" far and wide let me state the following; All tools require proper maintenance to perform at their peak for extending their life and reliability. I know what I am supposed to do, and most of the time do it. You'all clean them damn weapons on a regular basis, and they will be your best friends and not your demise!!! That said I don't know what all the fuss is about.... I have washed my truck at least 3 times in the last 9 years that i remember! and it runs just fine....so there![ROFL][gun]
  12. Seawolf1090

    Seawolf1090 Retired Curmudgeonly IT Monkey Founding Member

    Depends on the ammo - a lot of surplus tends to be 'dirty'. So, a good spray cleaner is necessary. The "Spanish Lady" is easy to field strip, and cleaning ain't hard - just takes some time. Thank Goodness we don't have a gas system to have to worry about!
    I have been reloading the surplus cases if I find them with boxer primers. My Aussie and Venezuelan CAVIM brass is reloadable.
  13. Sharpie44

    Sharpie44 Monkey++

    Ya I'm still working out the kinks in this rifle. I love it but I don't know how to oil and clean it properly yet. I'm just doing it the same way i would one of my bolt actions.

    I'm also having problems with the magazines. Once in a while the gun won't strip the next round out and just sit there with the breach half open with the round half out of the magazine. The New Aluminum mags i have work fine but the old beat up steel ones are hit and miss. I think I'm going to have to find a way to fix them.
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