caliber/mm conversion

Discussion in 'General Rifle Discussion' started by sniper762, Jul 30, 2012.

  1. sniper762

    sniper762 New Member

    644
    0
    0
    http://mdmetric.com/tech/cvtcht.htm/

    i thought a 7.62 x 51 = .308 cal.
    7.62 x 39 = .311 cal
    7.62 x 54r = .311 cal.

    the above conversion makes 7.62mm = .300 cal.
    neither .308, or .311 = 7.62mm
     
  2. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

    11,380
    1
    0
    We in the USA tend to measure bore diameter across the lands. The Europeans/Eastern bloc measure across the grooves. Trying to make sense of cartridge naming is an exercise in futility. The .44 Mag uses a .429 bullet while the .41 Mag uses a .410 bullet. The .38 Special uses a .358 bullet so it would more appropriately be called a .36 Special?
     

  3. 303tom

    303tom Well-Known Member

    5,172
    83
    48
    Don`t try to make sense of it, it will drive you NUTS...................
     
  4. locutus

    locutus Well-Known Member Supporter

    16,404
    276
    83
    Unfortunately there is no standard. We still have the .45-70, and the .250-3000.

    I've learned the system, but I gave up trying to understand it years ago!:D
     
  5. wpirate14

    wpirate14 New Member

    47
    0
    0
    Words of wisdom right there.
     
  6. c3shooter

    c3shooter Administrator Staff Member

    21,343
    214
    63
    do NOT assume that the system makes sense. Much of the naming was done by marketing departments after a 3 martini lunch. .50 Browning Machine Gun is NOT .50 inches in diameter. There are a handful of 9mms - many of which are NOT 9mm. .32 Short Colt and .32 S&W are not the same diameter. Neither is .22 LR and .22 Magnum. And yes, Americans measure a bore one way, Europeans another.

    Why ask why? Drink Bud Dry. :p
     
  7. primer1

    primer1 Well-Known Member Supporter

    9,734
    137
    63
    You've been there too?
     
  8. billt

    billt New Member

    1,642
    0
    0
    Lazzaroni has the most accurate MM designation. Their 7.82 Warbird is an honest .308 diameter. .308 divided by .03937 = 7.82 MM.
     
  9. locutus

    locutus Well-Known Member Supporter

    16,404
    276
    83
    But is that measurement taken from the lands or the groover??:D:p:D
     
  10. billt

    billt New Member

    1,642
    0
    0
    The 7.82 Warbird represents the bullet diameter of the round, which is .308.
     
  11. locutus

    locutus Well-Known Member Supporter

    16,404
    276
    83
    In that case, it should be the sdame diameter as the grooves.:p

    BTW, I was pulling your leg with the last post!:D:D
     
  12. billt

    billt New Member

    1,642
    0
    0
    Which grooves? The ones in the barrel, or the ones on the bullet after it comes out??? :D
     
  13. gunnut07

    gunnut07 New Member

    944
    0
    0
    Hum the 50 bmg is. 502" in dial. How is that not 1/2"?
     
  14. c3shooter

    c3shooter Administrator Staff Member

    21,343
    214
    63
    Actually, an UNFIRED .50 BMG has a max diameter of .510. On firing it is squeezed to .50.
     
  15. gunnut07

    gunnut07 New Member

    944
    0
    0
    Yes dang phone fat thumbs tiny keys. Need to upgrade to a galaxy s3....
     
  16. therewolf

    therewolf New Member

    8,409
    1
    0
    Get a good reloading manual by Lyman, Speer or Hornady, it will

    solve a lot of mysteries for you. Case in point:

    The .45 ACP vs .44 Rem Mag comparison-

    I shoot my .44 through one BBQ tank and make a

    massive dent on the next one, while a .45 only makes

    a dent on the first one.

    The manual points out that the .44 uses @ 5 times as much

    powder.
     
  17. billt

    billt New Member

    1,642
    0
    0
    A .500 S&W actually is .500.
     
  18. sniper762

    sniper762 New Member

    644
    0
    0
    wrong..........straight from a .50bmg barrel maker

    We make our .50 caliber barrels with a .500" diameter bore diameter and a .510" groove diameter. The twist rate options are 15" (for the 50 BMG cartridge) and 32" and 48" (for black powder guns and limited to 30" finish length).
     
  19. 303tom

    303tom Well-Known Member

    5,172
    83
    48
    See can`t none of ya make up your minds, told you it will drive you crazieeeeeeeeeeeeee.