Graphic Breakdown of .308 vs 7.62×51

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TriggerTimeTV shared a fantastic graphic showcasing the difference between the .308 and military-standard 7.62×51 cartridges. While some¬†shooters understand that .308 (the civilian standard) is actually more powerful than its military cousin, few likely know the actual differences between the cartirdges.

Full graphic is below and click on it to be taken to TriggerTimeTV on Facebook.

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Nathan S.

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

Nathan can be reached at Nathan.S@TheFirearmBlog.com

The above post is my opinion and does not reflect the views of any company or organization.


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  • USMC03Vet

    Can’t resize FaceDerp images on mobile.

    :[

  • Marc

    You can ignore these shenanigans if your rifle is CIP-proofed.

  • Axel

    Someone please explain to me why my truckload of German surplus 7.62 makes my Sako L579 bolt sticky to unlock. Usually I run it with handloads and norma factory ammo. The German surplus (MEN Eisenkern) runs very well in a Garand-derivative rifle that I shoot it with.

    • Axel

      W00t it’s even in the graphic! I didn’t know about the headspace difference!

      • dan citizen

        this graphic is mixing GO and NO-GO specs irresponsibly.

  • Jason

    PLEASE do further research on 308 vs 7.62 headspace. This is incorrect internet information presented as fact and sorry to say but the well done graphic here will only help to perpetuate the incorrect information.
    They are correct on #3 that military brass usually has thicker case walls than commercial, but their information headspace and pressure is wrong.
    There is a lot of incorrect information on the net about 308 and 7.62 and that was apparently their source of info. Consulting SAAMI and having researched industry standards, shows that they are comparing .308 Win GO headspace against 7.62 NATO NO-GO headspace. Bottom line the ammo is the same size, but the 7.62 NATO has a longer chamber NO-GO. The headspace ranges are overlapping .
    Also their pressure data is citing old CUP (copper crusher data commonly called PSI back in the day before they could actually measure PSI) for one and modern piezoelectric transducer actual PSI for the other.
    Nice work on the graphic by TriggerTimeTV, but please fix the technical content or take it down.

    • Wetcoaster

      The biggest issue I’ve heard of shooters running into is with M14-type rifles (Norcs and Springfields both up here) is the occasional OOB detonation with the softer .308 primers.

      • DrewN

        It doesn’t seem to be as much of a problem with the NM spec guns though, since they cycle so much softer. My SA M21 drops the brass right on the table all day long. I do shoot surplus ammo through my mil specs though, since premium ammo would be wasted anyway.

  • Zebra Dun

    I learn something every time I come to this site!
    This sounds similar to the .223 and 5.56 x 45 differences.

    • DIR911911 .

      as I remember it’s the opposite , 308 is higher pressure than 7.62 but 5.56 is higher than 223.

    • B. Butler MSG USA ret

      As long as you understand that the article does contain much untrue information. For reference, see the SAAMI website and appropriate specs therein.

  • lucusloc

    Link to original? The one on FB is a terrible size as well.

  • havoc

    After reading this, I was perplexed at how I missed this essential information being a long-time fan of the 7.62x51mm and 308 Winchester. So I looked it up in my Cartridges of the World 9th Ed.

    !?

    The information in this infographic does not comport with the information in CotW(9th).

  • Hunter57dor

    your pressure comparisons are misleading as well.

    while yes, the MaXIMUM saami pressure is lower on 7.62x51mm nato, the average saami pressure is identical. why?

    these tolerances are given out to manufacturing contracts to ensure reliability and safety in ALL nato firearms that may chamber these rounds, and as a safety buffer just in case of defects.

    .308 win ammo, being a more commercial variety, made in smaller batches, and typically including the selling point of being “higher velocity than the competition” have much higher allowable pressures.

    but apples to apples, it is going to average roughly the same, and in a properly proofed rifle, you should have no problems shooting either.

    That isn’t to say that you should trust all ammo regardless of headstamp, of course use the same caustions you would use with any other ammunition. But i do not think it is cause for undue alarm either

  • Lance

    Don’t matter a good semi auto like a semi auto FAL or M-1A can take both rounds.

  • McThag

    Welcome to August 2014…

    The max pressure for 7.62x51mm NATO is not 50,000 psi, it is 50,000 CUP. 50,000 CUP, in this case, is equivalent to 60,000 psi.

    Next, every weapon designed for NATO that fires 7.62x51mm NATO gets proofed with a 140% pressure charge. That’s 84,000 psi and the gun must not break to be accepted. That’s a pretty sizable safety margin.

    The 62,000 psi max pressure for SAAMI is intended to the the absolute limit with a 52,000 psi maximum average pressure.

    The differences in headspace has resulted in ruptured cases in some rare instances when .308 is fired in a NATO spec chamber.

    Another important difference between .308 and NATO is the leade. Mil guns tend to have longer leades and that tends to lower the actual chamber pressure in the gun. This is for reliability when the gun gets really hot.

    I guess the good news is with the ban on importing parts kits with intact barrels, most “7.62x51mm” battle rifles you’ll encounter are actually going to have .308 chamber dimensions.

    Anecdotally, when was the last time you heard of someones battle rifle blowing up where it wasn’t sketchy surplus ammo (which should nominally have been NATO spec to begin with) or a gross error on the reloading bench?

    If this was actually a real problem there’d be a lot more broken gun stories out there on the internet because every negative thing in the world gets a thread.

  • USMC03Vet

    Sweet! Thanks.

  • Jim_Macklin

    Keep in mind the M1 Garand rifle was supposed a .277 caliber but the large reserves of WWI .30/06 ammo prompted several years of work to re-engineer the Garand to .30/06 with the new M1 round, 172 grain BT. That bullet shot further than the available space on most National Guard ranges and the M2 round was developed.
    The Garand Rifle has a weak operating rod system and high port pressure will bend the rod destroying accuracy and reliability.
    When the Army was adopting the T44 with the M14 rifle, the goal was to have the same ballistics as the Garand M2 load so firing tables and ranges/ sights would all work.
    The WWII powders left about 12 inch of space in a .30/06 case and a better stronger case was needed for machineguns and rifles.
    Bottom line, military needs to wound enemy soldiers, sportsmen need to kill deer, bear, bison and moose as fast as possible.

    • Joe

      Please stop perpetuating the myth that ANY Military is tasked with wounding enemy soldiers. The sole purpose of a Military is to kill people and break things.
      That is all.

      • Mark R

        Here’s My $.02 worth. I own a M14 /M1A Bought about 4 years ago. Since their has been so much back and forth about .308 Vs NATO 7.62 on this site and all over the web , I decided to call Springfield Armory as of today 4/8/2015. I was told all non military M1a’s are chambered for .308 as well as NATO 7.62X51

        Any one with an original Military weapon should review what is posted here and the web and make your own decision. Springfield could not say if an original M14 Military Long Gun was chambered in .308 as the company has been acquired since they were producing Military M14’s

        PMC who advertises their Round as (.308 Winchester (NATO 7.62) says it will work in both chambers and the load pressure equals that of a NATO 7.62 @ 2750 FPS with a 147 Grain Bullet. Their round noes not have the NATO stamp on the rear which is a Circle with a Plus inside. The reason is that The country of mfg is not a signatore

        to NATO.

  • Major Nav

    The external dimensions of the two cases are exactly the same and use the same primers. 7.62 has thicker brass which decreases the internal volume and therefore takes less grains of gun powder. So, if you load both cartridges with the same type of powder, bullet, and primer, the 7.62 will have less energy than the 308 because of the different VOLUMES. That is the sole reason for the difference in SAAMI specs (per SAAMI).

    The rifles/barrels are the issue. Most 7.62 rifles are designed with extra head room inside the chamber. The thicker 7.62 brass will easily expand to to fill the void, while the thinner 308 brass MAY not. The brass may separate just below the shoulder and remain inside the chamber while the rest of the shell is ejected. The following round will jam into the brass still in the chamber and may or may not fire with potentially life threatening results.

    If your rifle is stamped 7.62×51 vs 7.62×51(.308) or .308, you have to check your owners manual and then your own rifle and see if the headspace exceeds the .308 NOGO threshold.

  • hANNABONE

    just pickup a Rock River Arms LAR 8 and you can sling brass from either side of the ammo size fence. It likes .308 & 7.62 – Simple.!!

    • Ergo

      RRA can’t use lr308 pmags

      • hANNABONE

        tru dat…and that isn’t a deal breaker for me. Believe me, I’d love it if they’d accept Pmags and the like – but….well, I’ll take the RRA durability and craftsmanship and accuracy and gulp hard on that nano point.

        • Ergo

          Not having access to a high quality polymer mags or new production metal mags is a deal breaker for me. Used fal mags or thermolds don’t entice me to buy into a system.

  • parlayer

    The 7.62 I shot in the US Army (M-14) did not have a number behind it?? Still an excellent caliber. is that # for an AK? if not what? Anybody??

  • Ganderite

    I have worked in a ballistics lab and have pressure tested thousands of rounds of both types of ammo. As has been noted, the pressure limits of both ammo are about the same. I have seen several lots of Winchester match over 60,000 psi and at least one lot of military ball over 60,000 psi. Most ammo (military and civilian) is in the 57,000 psi range.

    At one time NATO specs quoted a max pressure of 50,000 psi. What they really meant was 50,000 cup. This has lead to the confusion.

    • Major Nav

      PSI and CUP have nothing to do with the issue.
      It’s purely headroom of any specific rifle and whether or not the brass you are using can survive expanding into that headroom.
      7.62 spec ammo can and 308 spec ammo might not.