7.62x51 vs. 7.62x39

Discussion in 'General Firearm Discussion' started by Confederate Hammer, Feb 16, 2012.

  1. Confederate Hammer

    Confederate Hammer New Member

    Messages:
    14
    Likes Received:
    4
    Location:
    Virginia (for now, and for the past 33 years)
    Feedback:
    0   0   0
    Now, before anyone jumps all over me about the title of my post, I know the difference between the two calibers.
    I just want to know - if a 7.62x51 is a .308, what would a 7.62x39 be?

    BTW, I love an AK :D for oh, home defense (need to find some frangible ammo for AK), hunting (have some Cor-bon and Hornady hunting ammo) , target shooting, plinking.
    I've modified my AK to be a homeland defence rifle, I've installed a skeletonized sniper stock, grip pod bipod, and a 4x scope.
    In keeping with homeland defence theme, I also have 15 thirty round magazines, 10 ten rounders, and 1 seventy five round drum.
    So if any foreign troops wish to invade the US, I can help repel them (even though my AK isn't select fire).

    And BTW, the AK-47 rifle as designed by Mikhail Kalashnikov is as bulletproof as it's rumoured to be, I've owned my AK since '96 or so and just now cleaned it for the first time (15 years later).

    It's never misfired, jammed, or had any other malady associated with not cleaning your weapon.
  2. Toxic6

    Toxic6 Active Member

    Messages:
    736
    Likes Received:
    153
    Location:
    Higher then a PDX hipster (~10,000 ft higher)
    Feedback:
    42   0   0
    "if a 7.62x51 is a .308, what would a 7.62x39 be?" a .311 carbine.....?
  3. DieselScout

    DieselScout Well-Known Member

    Messages:
    1,810
    Likes Received:
    1,017
    Location:
    S Clackamas County
    Feedback:
    7   0   0
    You do know the second number refers to the length of the casing right? In the case you've listed, there is a difference in bullet diameter as noted above. Don't forget the 7.62x54R, uses a .311 bullet and is a rimmed casing.
  4. Confederate Hammer

    Confederate Hammer New Member

    Messages:
    14
    Likes Received:
    4
    Location:
    Virginia (for now, and for the past 33 years)
    Feedback:
    0   0   0
    Right.

    Okay, but my main question still is: what makes a 7.62x51 a .308? and what mathematical calculations do I use to come up with that :huh:
    And what would a 7.62x39 be?
  5. sadiesassy

    sadiesassy Active Member

    Messages:
    557
    Likes Received:
    47
    Location:
    Prescott
    Feedback:
    0   0   0
    If the first numner is the diameter and second number the length - Why are they not both the same with length being different.

    Second question: 7.62 is mm diameter - right - which is 0.30 not .308.

    SO why is it .308 or .311?
  6. JGRuby

    JGRuby Banned

    Messages:
    1,137
    Likes Received:
    402
    Location:
    Portland Oregon
    Feedback:
    8   0   0
    I will admit I dont know the answer to your question but that is why I have realoding manuals for such information. It may have something to do with the 7.62X39 being of european descent and that is how they created it over there - the 308 is an American creation and that is how we do things over here. I dont know why but I know that this distinction can be very important.


    James Ruby
  7. krivey

    krivey Member

    Messages:
    131
    Likes Received:
    24
    Location:
    mcminnville oregon
    Feedback:
    5   0   0
    7.62 is a general classification for a .30 caliber. There are many 30 cal that have slight variations in diameter. The ".308" is the name given to the commercial version of the 7.62x51. Most names given to cartridges are not exact in the size of diameter. Look up each individual catridge specs and you will see the names of the cartridge are different from the actual size. Naming a cartridge is just a name that gives you an idea of what the round is.
    Nwcid, Blitzkrieg, chemist and 3 others like this.
  8. mjbskwim

    mjbskwim Well-Known Member

    Messages:
    5,561
    Likes Received:
    1,657
    Location:
    sequim
    Feedback:
    12   0   0
    What krivey said,it's marketing.Like calling your 347ci engine a 350


    So the answer to your question is.......







    Whatever you want it to be called
  9. jerman1964

    jerman1964 Member

    Messages:
    515
    Likes Received:
    14
    Location:
    Sherwood, OR
    Feedback:
    45   0   1
    True, but in this case, the 7.62 nato is in fact 308 thousandths in diameter, the 7.62 soviet is 311 thousandths of an inch. Ruger in his wisdom made the mini 30 .308 for bullet selection, thinking that the 3 thousandths of an inch wouldnt effect performance. The same in the 9mm (.355) and the .357 blackhawk convertible. The .45 lc and .45 auto are also off by a couple thousandths of an inch, .454 vs .451
    Boedy and (deleted member) like this.
  10. mjbskwim

    mjbskwim Well-Known Member

    Messages:
    5,561
    Likes Received:
    1,657
    Location:
    sequim
    Feedback:
    12   0   0
    Just dump a little more powder in ,it will go.
  11. jerman1964

    jerman1964 Member

    Messages:
    515
    Likes Received:
    14
    Location:
    Sherwood, OR
    Feedback:
    45   0   1
    thats true, but sometimes the way it goes is not as much fun as others. True story, an NRA firearms instructor had one of his people accidentally chamber and fire a .308 round in his .270. It did go.....
  12. pokerace

    pokerace Gold Supporter Gold Supporter

    Messages:
    1,966
    Likes Received:
    499
    Location:
    Newberg
    Feedback:
    29   1   0
    what would a 7.62x39 be?
    30-30
    pdxPope and (deleted member) like this.
  13. unklekippy

    unklekippy Well-Known Member

    Messages:
    1,329
    Likes Received:
    856
    Location:
    In The Mountains Near Sprague River
    Feedback:
    25   0   0
    .308 is an American measurement(Y'know, inches, feet, miles and such). 7.62x51 is the metric measurement(centimeters, meters, kilometers and such) for the rest of the world. The 7.62x39 was for a long time a Soviet weapon, hence the metric designation.So, if you call it 7.62x51 and not .308, you are the invading army. Calibers make no sense. Example: 9mm, .380, .38 and .357 are all in fact .357 in diameter, but naming them all .357 may get confusing as well. Kip
    borrowedsig and (deleted member) like this.
  14. unklekippy

    unklekippy Well-Known Member

    Messages:
    1,329
    Likes Received:
    856
    Location:
    In The Mountains Near Sprague River
    Feedback:
    25   0   0
    Ballistically, the x39 is almost identical to the 30-30.You cannot chamber the same, the way you would 7.62/.308 or 5.56/.223. Kip
  15. JGRuby

    JGRuby Banned

    Messages:
    1,137
    Likes Received:
    402
    Location:
    Portland Oregon
    Feedback:
    8   0   0
    Had a good freind do the same thing one day out to DRRC - he was hooting his Model 88 in 308 and loaded one into his CZ550 iin 270 winchester - he touched it off - made a unique sound and we could not get the bolt open - later that day we opened the bolt using a 2X4. Long story but the action was magnafluxed and headspaced - he is still shooting it today with 270 Win with no perceivable changes. Learned alot that day - the CZ550 is a fine and tough rifle - and only open and shoot one gun with one box of ammuition at one time off the bench.

    Firearms is really a bad hobby to be dumb in - the cost for ignorance can be very high.
    We all make mistakes - most of the time we get away with it.

    James Ruby
    jerman1964 and (deleted member) like this.
  16. JohnnyCauc

    JohnnyCauc Member

    Messages:
    43
    Likes Received:
    8
    Location:
    Portland, OR
    Feedback:
    3   0   0
    It really does come down to the variation in design as to what parameter was used to measure the caliber.
    Also worth noting is that caliber is often a measure of land diameter, not groove diameter, so a 7.62x39mm/7.62x54mmR bore diameter is indeed 7.62mm (.30, inline with the old 3-line designation) at its narrowest, but the grooves are 7.92mm, so the bullet diameter needs to be larger than the narrowest measurement of the bore.
    7.62x51mm is actually a .308 (7.82mm) bullet diameter.
    Again, it's just what point was used for measurement, much like the 45 Colt/.45ACP and 9mm variations mentioned above.
  17. DoubleTapDrew

    DoubleTapDrew Well-Known Member

    Messages:
    1,081
    Likes Received:
    379
    Location:
    Oregon
    Feedback:
    1   0   0
    Was told a while back the reason the russian 7.62 is .311 is they take the measurement from inside the rifling while the U.S. doesn't include the rifling in the measurement. Dunno if that's correct or not but it made sense at the time.
  18. Nwcid

    Nwcid Moderator Staff Member Gold Supporter

    Messages:
    3,452
    Likes Received:
    1,344
    Location:
    Yakima and N of Spokane
    Feedback:
    19   0   0
    You have gotten lots of good answers here.

    The very simple answer is in the US we just make up names for cartridges for the most part, or keep the names really short. Many of our rounds start with the caliber (diameter measured in inches) like .30 (for .30 caliber). In .30 caliber we have TONS of guns, .30-30, .03-06, .308, .300 Win Mag, .30-378, ect, .300 Whisper aka Fireball aka BLK aka many others. Or .357 mag, .38 super auto, .38 special, ect which again all are the same diameter bullet.

    In the European countries they use bullet diameter and CASE length (not overall length) in metric. So for .30 caliber they call it 7.62. So ALL of their .30 caliber guns including pistols have names like 7.62x25, 7.62x39, 7.62x51, 7.62x54r (r is for rimmed rounds). They dont come up with cool little marking names like we do.

    Here is some more on the topic, 7.62 mm caliber - Wikipedia, the free encyclopedia
    Here is another example of all the guns that use a 9mm size bullet, 9 mm caliber - Wikipedia, the free encyclopedia Yet generally when we say 9mm everyone things 9mm Luger.
  19. hermannr

    hermannr Well-Known Member

    Messages:
    1,851
    Likes Received:
    900
    Location:
    Okanogan Highlands
    Feedback:
    0   0   0
    As was noted before, 7.62 is european metric, .308 is inch and US British and Canadian.

    My favorite is the 7.62mm X 25mm, which of course is a handgun cartridge. Also, 9mm actually is .355 not .357 but basically still 9mm "X" any number is a European cartridge. .357 is an american designed cartridge The .357 mag AKA 9X33R in Europe, In general, if you see an "R" in the designation, it is a cartridge designed under the "inch" standard, but converted to metric measurements for the european market. 357 Sig is a 9mm from a Europen firearms manufacturer, but the cartridge design is from an american manufacturer (federal) hense the .357 rather than 9mm. It actually take 9mm (.355) bullets.
  20. trainsktg

    trainsktg Well-Known Member

    Messages:
    2,591
    Likes Received:
    709
    Location:
    Portland OR
    Feedback:
    59   0   0
    Let's not forget 7.62x5r (Finn) or 7.62x45.

    I think 'R' stands for 'rimmed', at least with military rifle ammunition. 7.62x54r, 7.62x53r, 8x50r and 8x56r are all rimmed cartridges.

    Keith