.308 Winchester vs. 7.62×51 NATO

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Ever wondered about the difference between the .308 Win and the 7.62×51 cartridge?
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From 6mmbr.com

Before we go much further, we want to address the oft-posed question “are the .308 Winchester and 7.62×51 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 7.62×51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win “Go Gauge” is 1.630″ vs. 1.635″ for the 7.62×51. The .308′s “No-Go” dimension is 1.634″ vs. 1.6405″ for a 7.62×51 “No Go” gauge. That said, it is normally fine to shoot quality 7.62×51 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 7.62×51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max.

A UK armourer explains the problems he had using reloaded cases fired from military 7.62×51 rifles in his .308 rifle:

Around this period I discovered that shooting reloaded cases fired from an FN was virtually impossible. They didn’t want to chamber. My frustration led me to ask an older armourer what was wrong. In a nutshell, he told me that they probably didn’t fit because they stretched. I was using a Lee Loader in 308 Winchester and didn’t know that they only resized the neck, leaving the rest of the case untouched. The shoulders were blown forward on initial firing, so the case was simply too long to fit my rifle’s chamber! Hmmm…

More here.

Some more more information here:

Difference between .308 Winchester & 7.62x51mm NATO?

Related

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


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  • james hodkinson

    Hi writing from South Africa I just want to know can a AK47 fire ether a 308 or 303 round?
    thanks James

  • http://www.thefirearmblog.com Steve

    Hi James. There are AK clones, such as the Saiga 308, that fire .308.

    I don’t think there have ever been a .303 clone as it is a rimmed cartridge.

    Are civilians allowed semi-auto rifles in South Africa?

  • chad

    If you have any ak or variant with 7.62mmx39mm stamped on it then, NO, , the .308, .303, won’t chamber. and may blow the holy hell out of that AK. You COULD, reload the 7.62x39mm bulluts into .303 cases.. They are the sme diameter (.311) .308 bullets are (.30 cal). Also, and i want to say dont try this at home, but i have by accident fired a 7.62x39mm through a smle #1 mark 3 and it just landed about 2 inches high at 50 yards. I wouldnt advise it, but i wonder how much that has been done in afgahnistan.?

    • Frosted Fur

      I tried to chamber a X39 in my SMLE and I couldn’t close the bolt. So how in the he’ll did you get it to fire?

  • Walter Brunner

    62,000 psi vs. 50,000 CUP.  Same pressure, different measuring method.  Semi-automatic and automatic weapons need more cartridge-to-chamber clearance than bolt actions, hence Winchester could tighten the head space for the .308 WCF.  If anything, a max size 7.62×51 cartridge may be hard to chamber in a .308.   Anybody attempting reloading ought to do just a bit of reading beforehand, so he wouldn’t have to wonder aloud why his Lee loader won’t produce ammo that can be chambered in another rifle from cases fired in an FAL.  Duh! To James:  Not unless you chamber it with a hammer.  A .303 would enter the 7.62×39 partway, but the bolt wouldn’t be able to close.To Chad:  “Accidentally” fire a 7.62×39 in a .303?. Nasty little bugger just snuck into the chamber when you weren’t watching?. You wer lucky you didn’t get a faceful of brass and hot gas.

    All you guys for real????

  • JJ

    I could use some advice about a different angle on the same question.

    I have access to a lot of factory new .308 Win but am short on linked 7.62 for use in a MAG-58.

    It occurred to me that I could hand link some of the .308 to fam-fire the MG. The heavier barrel and chamber should easily handle any difference in the pressures but I am not an expert, just a shooter.

    Am I setting myself up for failure?

    Everything I have read online pertains to .308 vs 7.62 rifles.

  • Jim Lawson

    Heres an accidental, but instructional event that happened to me. I reload for .308. I shoot two rifles M1A and Savage 10FP, both in “.308″. Recently while shooting the Savage I had brought along some reloads that were “fire-formed” in the M1A. I did not do this on purpose and did not realize it until I went to chamber a round in the Savage. Nope, not happening! Chamber Pressures aside, the Mil-Spec chambers are dimensionally longer, You cant tell the difference looking at the cartridge, and even with a good caliper, its probably not very easy. That “.003″ inch of difference is all it took, in practice, to finally make me a believer that these 2 cartridges, 7.62×51 and .308 are not dimensionally the same.

  • http://www.thefirearmblog.com Steve

    Jim, very interesting!

    • k. rowe

      Must have neck sized only.Even if you tried them in another M1A they may not have chambered if its chamber was much tighter.

  • Jim Lawson

    Steve,

    Thanks, Yes it was interesting because the case necks were trimmed, so it was the movement of the shoulder of the cartridge forward during the “fire-forming” process in the M1A that changed the dimension. Also, I can take a cartridge “fire-formed” in the Savage, neck trim it to proper case length, reload it, and still use it in the M1A. I had read about the .003″ (longer) difference in mil-spec chambers, but this proved that some 7.62×51 designed cartridges really could be “too long”, (.003″ longer) for a commercial .308 chamber. Staring at the two cartridges will not convince you, at least it did not convince me, but this did.

    So my rule of thumb is, in general, if you reload:

    You can reload cases fired in a .308 commercial chamber for a milspec chamber, but you cant do the opposite. Once its fired in a milspec dimensioned chamber its now what I would call “7.62 dimensioned”.

  • Dick

    As an old Army veteran, I believe that we’re mixing chamber dimensions and cartridge dimensions. Within reasonable manufacturing tolerances, 7.62 mm NATO and .308 Winchester cartridges are identical. Military chambers are cut a little long to guarantee cartridges from any manufacturer will readily chamber. A firefight is a bad time for a jam from an oversize cartridge to occur. Civilian chambers can be cut tighter without negative consequences. Chamber pressure limits are the same for both cartridges — lbs per square inch (PSI) and copper units of pressure (CUP) represent different pressure measuring techniques and different pressure scales.

    • k. rowe

      SorrY,replied to wrong post

  • Kirk,

    Ive got an Ishpor 308 nato
    and i tried the winchester 308 in it,
    no way it dosnt work,
    too tight on the shoulder and then it gets stuck in the bore,
    where do I get ammo for this rifle, so i can enjoy shooting it,

    • louis

      i had an ishapore enfield that did a box of 308win white box thru no probs but after reading decided on strict .308 nato (7.62×51) diet. american eagle, win white nato, silverbear brown etc.

  • fadedtrends

    to kirk. it’s 7.62 Nato, sorry a pet peeve of mine. I too have and Ishy and it chambers and fires .308 win just fine, although as time, experience and reading countless literature I’ve come to realize that I need to Find 7.62 nato rounds for my ishy. I do still shoot 150gr .308 win rounds, I tried larger grain bullets and experienced cases getting stuck, my theory is the hotter rounds caused more expansion, I’ve had good luck with Wolf, Privi Partisan, S&B, Brown Bear, silver bear and Winchester and Federal all between 145 – 150gr bullets, my reloads stay between 2600 and 2700fps range, I have Winchester 147gr 7.62 Nato rounds on order and I will see how those work.
    I’m afraid all this gun will be for is just plinking, which is a shame as I get decent groups at 100yds for what I paid for it.

  • http://none MG.

    I got rid of a Winchester pre-64 in .308 that would get 7.62×51 brass hung up in it after I fire the cartridge! It didn’t happen all the time, but only with 7.62 NATO cartridges. The case neck-end was a little ragged. A gun smith said that it needed to have the chamber reamed out a little bit. He called it a universal 7.62/.308 chamber. Is this what you guys are talking about with 7.62 brass being longer?

    MG. (It cleaned up the 7.62 accuracy and extraction problems. but hurt my .308 accuracy and velocity)

  • JTN

    The 308 Winchester and the .62 NATO round are the same. I can’t believe someone said that the military rounds/ weapons stretched the shell casings. Just about all centerfire rifles stretch the shell casings eventually. That is why case trimmers were invented. By the way there is no such thing as a 7.62X51 NATO round. The 7.62 NATO round is always 51mm long. Any other length is not a 7.62 NATO round. It is something else. For example, a 7.62X39 is NOT NATO.

  • James

    JTN – The cartridges are the same for all intents and purposes, aside from the fact that most milspec ball ammo uses cases with thicker walls than commercial brass that result in higher chamber pressures, BUT milspec semi-auto chambers, at least up to the M14, and probably the new M110 that is going to start being issued, have slightly larger chamber dimensions. If you fire a round in a milspec 7.62×15 (.308) chamber, the shoulders of the brass, will move forward further than if fired in a Remington 700 7.62×51 (.308) chamber that was cut commercially. Ive proved this to myself time and again. M14 (I cant vouch for the M110 i.e. AR-10) chambers are longer, than their commercial bolt action counterparts.

    Yes all rifles stretch the “neck” of a case, but milspec M14 chambers will mover the shoulder farther out.

    Also, in reference to 5.56×45 (.233) thats why we have something called a “Wylde” chamber, because there are minute tolerance differences between military loaded ball ammo and the standard .233. Look on the receiver of any Wylde Chambered AR-15. It will say 55.6/.233.

    All in all, military chambers must be slight larger (and we are talking about fractions of inches) to account for discrepencies that often show up in mass produced military ball ammo.

    Your comment about NATO and naming convention really has no bearing on any of this. Leave the “x51″ attached to “7.62″ or not, it is a .308 bullet and the case is 51 mm, They are exterior dimensionally the same.

    BTW, neck trimmers don’t move shoulders back in case you havent figured that out yet. Go grab some old Lake City 70 that has been shot in M14, full length size it, trim the neck, load it up, and see if it fits in your 2009 Remington Sendero. Chances are, you wont be able to close the bolt without much force.

  • James

    BTW anywhere I wrote 7.62×15 was a typo. I meant 7.62×51

  • James

    .308 Win vs. 7.62×51–The Straight Scoop
    Before we go much further, we want to address the oft-posed question “Are the .308 Winchester and 7.62×51 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 7.62×51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win “Go Gauge” is 1.630″ vs. 1.635″ for the 7.62×51. The .308′s “No-Go” dimension is 1.634″ vs. 1.6405″ for a 7.62×51 “No Go” gauge. That said, it is normally fine to shoot quality 7.62×51 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 7.62×51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max. For more information on this interesting topic, read the following articles: Gun Zone’s 30 Caliber FAQ; Cruffler.com Technical Trivia, June 2001; and last, but not least, Steve Redgwell’s .308 vs 7.62×51 Analysis, which really provides a definitive explanation. Reloaders should also note that military ammo often is made with a thicker web. Consequently the case capacity of 7.62×51 brass is usually less than that of commercial .308 brass. You may need to reduce recommended .308 Winchester loads by as much as 2 full grains, if you reload with military 7.62×51 brass, such as Lake City or IMI.

    from http://www.6mmbr.com/308Win.html

  • Gordon Dempsey

    .308 Vs. 7.62×51
    Why are the chambers of different types of rifles always looked at when looking at these guns. What is the chamber for the sniper rifle compared to the bolt gun? Are the specks still that far apart? How about operating pressures?
    Yes, the camber on battle rifle is oversized to allow cheaply made/ dirty components to work.
    On reloading, one must adjust the bullet to the gun/ chamber. I have loaded ammo for my rifle that would not work in another rifle of same make and brand. Mine had a looser chamber than the other did. Even though it was still in speck for my gun, it was not in for the other.

  • MG.

    The SAAMI/CIP pressure for .308win. is 62,000psi and the 7.62x51mm should read 50,000 CUP (Copper Units Pressure) or “Crusher Method”! For the first time I saw external 7.62x51mm NATO Specs. published on Wikipedias 7.62x51mm cartridge link by Winchester and Rad-Way. These two cartridges are in deed different!(COL. Cartridge Over-All Length, Neck Dia. and Case length). As far as the chamber differences between the .308win. and the 7.62x51mm are concerned, some military knuckle heads will try to tell you that they opened up the tolerancs for delinked machine rounds! The only problem with this statement is that Remington made their M700 in both chamber dimensions! You may as well just say that Remington made the mistake instead of the military……NOT!!!!!!

    MG.

  • Brendan Berube

    I have ordered, and will hopefully be receiving soon, a Chicom Poly M-305B chambered in 7.62×51 from a reputable Canadian dealer. Why would I order such a firearm? Because it is inexpensive to purchase and I intend to operate it very cheaply with hand loaded .308 ammo for target shooting and plinking.

    I will, however, measure its chamber head space prior to ever shooting it, with my Forster .308 gauges. If it swallows the ‘no go’ .308 gauge I will return it without firing a single shot. If the chamber is cut tighter than this, I will then fire 5 shots and run the fired cases through my RCBS precision micrometer to get a more accurate estimate of actual chamber dimensions. If I am happy I will keep the rifle. If not I will return it. I will never load a bullet heavier than 168 grains, and most of my loads will be with 150 grain bullets. Just to be on the conservative side of things, I will never load beyond the starting loads for .308 Win. and will use a .308 full length die. I may even crimp my bullets. The gun will tell me what to do in this regard.

    Here it is then. Commercial .308, and most well made domestic 7.62 ‘NATO’ ammo, is pretty well identical in exterior dimension in my estimation. New unfired cartridges in either loading will readily chamber in either a .308 Win. or a 7.62×51 chamber. ‘NATO’ manufactured chambers can, and do, vary by age of manufacture, use, and by manufacturer. What you get is what you get. If you are willing to carefully assess the actual chamber dimensions of your NATO chambered rifle, you may well find you have a suitable gun to shoot .308 cartridges in terms of acceptable head space dimension. If not, don’t do it. Simple.

    As for the .308 vs 7.62 NATO pressure issue, I personally believe that in 1954 when the military adopted the 7.62×51 as a standard, there was no piezo PSI pressure measurement equipment/protocol available. Therefore, when you hear someone say (authoratatively) that military 7.62 NATO ammo produces 50,000 PSI, what they really should be saying is that it produces 50,000 CUP (copper units of pressure) which was the measurement protocol back in the day. This has been determined, I believe, by modern day test equipment, to be almost the same as modern .308 ammo PSI. This should be the only area of debate on this issue really, based on what you believe. Do both cartridges produce similar pressures (in a standardized chamber) or not? I believe they do.

    Chamber dimensions between .308 Win and NATO 7.62×51 will differ. In some instances to a dangerous degree. Case volumes between the two cases are different. Load accordingly. Are pressures pretty well the same in the same test chamber? I believe so. Some will even tell us that NATO rounds are sometimes ‘hotter’ than commercially loaded .308 cartridges.

    If you are uncertain about a particular endeavour in the firearm arena, err on the side of safety and get a professional opinion before doing it.

    Safety first.

    • k. rowe

      you’ll probably be sending it back then
      A .308 no-go is smaller than the nato go gage
      . If you asked for a nato spec chamber and get it why should they have to refund your money

  • MG.

    Brendan,
    I agree with your safety procedures and your analysis. I’ve been through what you are doing. I had two STG 58 rifles built by Enterprise back when they had really good recievers. They implored a universal chamber cut that gives you a “GO” condition for both .308win and 7.62×51. Hoever, I still shoot tighter groups with the 7.62×51 ammo. I sold my .308 win Remington 700 ,because surplus ammo wouldn’t extract all the time. With the cartridge over-all length being at least .050″ longer between .308 and 7.62×51 ,you can see the problems that can arise as far as accuracy and performance are concerned. I got a 30-06 Remington 700 which is a more accurate higher performance huntinting cartridge anyway! According to Winchester a 30-06 180gr. Ballistic Siver tip will deliver 29% more muzzle energy or terminal ballistics at 300yds. as compared to a .308win 180gr silver tip will. I stick to just 7.62×51 and don’t have anything to do with the .308win. anymore. God Bless and good luck with your endeavor!

    MG.

    • k. rowe

      You’ll probably be sending it back then. A .308 no-go is smaller than the nato no-go. If you asked for a nato spec chamber and get it why should they have to refund your money

  • GaryP

    I recent bought 500 rounds of surplus M80 ammo. Does anyone know what the “SBS” on the head stamp stands for? I assume that is the manufacturer but can’t find a list of manufacturers and their associated codes.

  • Mike

    SB is Sellier & Bellot – I don’t see an SBS, but it could be a third S&B location (SBP is prauge, main location is in Germany)

    Military weapons have slightly larger chambers to ensure chambering of different lots of ammunition AND to facilitate chambering when the weapon is dirty, fouled, etc after hundreds of rounds. This is especially true in automatic weapons (MGs, etc) which makes cartridges fired from a military weapon more difficult or impossible to re-load for a commercial chamber.

    The two pressure cites are in different scales. Some folks have noted this and the fact that they are equivelant, while there have been a few who still think 62,000 PSI is higher than 50,000 CUP, which is not correct. The two are effectively the same pressure. You should be able to fire any commercial or mis-surplus in a 7.62mm NATO weapon, but do not expect to re-load it for a commercial .308 Win changer without additional re-sizing. And don’t bother buying ‘once fired’ surplus 7.62mm brass, because it’s 99% likely to have come out of an MG and those weapons have even larger chambers making re-loading even more problematic.

    • alpinu

      Gentlemen,

      SBS stands for SANTA BARBARA SISTEMAS, the old state owned Spanish military manufacturer, it has nothing to do with SELLIER&BELLOT. SELLIER&BELLOT’s acronym is S&B, it is only located in Vlasim, Czech Republic, it has no location in Germany.

      SBS is now part of General Dynamics.

    • Albert Head

      If you’re full-length re-sizing (which 99% of people will be), the oversized cases of MG-fired brass isn’t an issue.

    • triggerfoot

      I reload for my 308, and milsup brass works great as long as you resize and trim. full length resize. load 2gr below max, and you should be good to go .500 round and no mishaps, or pressure signs

  • http://www.dvdandblueraydiscountreview.info Evangeline Clark

    Thank you for your post. Awesome.

  • steve

    This post is stupid. Its been proven many times over that the old 50K CUP is not a direct comparison to the commercial 60K PSI. Worse yet is direct translating CUP to PSI.