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Ammo sizes and differences in English vs Metric designations.

Discussion in 'The Powder Keg' started by Mike82, Jun 10, 2009.

  1. Mike82

    Mike82 G&G Newbie

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    Calibre:

    American standard: bullet groove diameter, uses inch convention.
    European standard: bullet land diameter, uses metric convention.

    Cartridge:

    You have many American rounds that have simply the calibre and designer, such as Remington, Winchester, Marlin, Hornady, PPC, Casull, etc.

    You've got many older rounds which used the convention of xx-yy or xx-yy-zzz, where xx is the calibre, yy is the powder charge, and zzz is the bullet weight in grains. Such as .45-70 gov't or .45-70-450, or .30-30 winchester, or .32-20, .25-20, .38-55, .38-40, .44-40, etc. The dashes are not pronounced; for example ".45-70" is just "forty five, seventy", not "forty five dash seventy". The gov't on the end of that one designates it as an official government (U.S. military) round.

    You've got European and military rounds with the convention of aa x bb mm, where aa and bb are both millimeter measurements, and aa is the bullet land diameter, and bb is the cartridge case length from back to front, such as 7x57mm mauser, 6.5x55mm swede, 7.92x57mm mauser, 7.62x51mm, 5.56x45mm, 7.62x39mm russian, etc. The "x" in these is read "By", as in "seven by fifty seven millimeter mauser", etc.

    Then you've got some oddball ones that start with the bullet diameter in inches or mm, but then use a random designation which one must learn on a case-by-case basis, such as .30-'06 springfield, which means .30 caliber (actually .308 caliber), adopted officially in 1906 in that particular loading, by the U.S. government as the standard small arm/rifle round, and springfield added on the end because the U.S. arsenal in Springfield was the place where the round was created/adopted. Quite a few other off-the-wall designations as well. Many rounds have multiple names with both an American and European version of the name. For example, the .380-auto in the U.S. is .380-auto or .380-acp or 9mm Browning short. In Europe it is the 9x17mm or 9mm Kurz. The 38 is actually .357 calibre, like the 357-magnum. The .38 Special and the .357 Magnum do not shoot the same bullet as the 357 SIG however, the 357 SIG shoots .355 calibre (9mm) bullets. The .44 Rem Mag is actually .429 calibre. The .45 ACP is .451 calibre. The .458 Winchester is .458 calibre. Same with .50 calibers. The .50 Action Express pistol cartridge is .50 caliber while the .50 Browning Machine Gun is .510 caliber. You have cartridges named after people, .257 Roberts, .35 Whelen, etc. The .35 Whelen takes .358 caliber bullets rather than the .355 caliber bullets of the 9mm. You have cartridges named after gun magazines, Mr. Simpson's Shooting Times Westerner and Shooting Times Alaskan cartridges; there are cartridges named after the class of weapon they were created for, like the 10mm Auto, and combinations of all of these, like the .32, .380, and .45 Automatic Colt Pistol. The .30-40 Krag was named after the inventor and designates a .30 caliber cartridge with 40 grains of powder. The .30-06 Springfield designates caliber and year adopted instead of powder.

    Conversion can be an interesting venture also:
    (These measurements taken from list of ammunition that has both Metric and Standard sizes)
    Measurements rounded to nearest thousandths.

    6mm & .243 calibre calculates into .236
    6.5mm = .257 calibre calculates into .256
    7mm = .284 calibre calculates into .276
    7.62mm = .308 calibre(except Russian, it is actually .311 calibre), calculated it's .300 calibre.
    8mm = .323 calibre calculates into .315
    8.6mm = .338 calibre calculates into .339
    9mm = .355 calibre calculates into .354
    10mm = .40 calibre calculates into .394
    11.46mm = .451 calibre calculates into .451
    12.7mm = .50 calibre calculates into .50

    After doing conversions though, you will start noticing some inconsistencies.

    To convert Standard(inch) to Metric(mm), multiply 25.4(number of mm in inch) by the number in inches(don't forget the decimal; example: 25.4mmx.50cal=12.7mm). To convert Metric(mm) to Standard(inch), divide the Metric size by 25.4(example: 12.7mm divided by 25.4mm= .50in.)



    In short, the designations given by the manufacturer are just approximations.

    Hope this helps anyone who needs to know how to convert ammo sizes, and for anyone who didn't know which same sized bullets were actually same size, or different.

    -Mike.
     
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  2. Cyrano

    Cyrano Resident Curmudgeon Forum Contributor

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    This is why reloaders slug their guns and then load the appropriately-sized bullet for their actual bore in the reloading press. It's the difference between an off the rack, ready to wear suit and a suit made by a bespoke tailor.
     
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  3. Mike82

    Mike82 G&G Newbie

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    correct Cyrano....and will you look at that, i wrote a longer post than you. :09:
     
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  4. Oxford

    Oxford G&G Evangelist

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    Excellent post, Mike82! Getting that information is a challange. Ammo doesn't seem to have been standardized like some other mechanical devices.
     
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  5. eagle4g63

    eagle4g63 G&G Newbie

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    Nice post you left out the steyr 8mm which is actually .329 not the .323 like other 8mm, just for shits-n-giggles!
     
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  6. Mike82

    Mike82 G&G Newbie

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    the ones listed were part of a mental list i thought up, of course i couldn't find info on all in the list....forgot the steyr tho....and couldn't find the designation on the carcano(at least the actual designation).
     
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  7. jsmaye

    jsmaye G&G Newbie

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    It's not 8mm. It's 7.92 mm.

    Mike82 - what's all this talk of "calibre"? You're in Georgia. It's "caliber". ;)
     
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  8. Mike82

    Mike82 G&G Newbie

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    jsmaye....i'm not in georgia....close, but not quite....and i use the old english spelling of words....got used to it and now people just think i misstype....of course, that many times can't be excused lol
    honor = honour
    caliber = calibre
    bearfluffernatore = tex
     
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  9. cremley

    cremley G&G Enthusiast

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    Hahahaha!!
     
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  10. jsmaye

    jsmaye G&G Newbie

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    I just figured you were being aristocratic. My spell-checker's the one that thinks you mis-type.
     
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  11. Mike82

    Mike82 G&G Newbie

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    hahahaha....i see, so you DIDN'T catch the spellings....mwehahahahaha....my spellings can fool humans....but not machinery, seems i need to adjust that. (didnt have enuff coffee with my cream and sugar this morning :09: )
     
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  12. jsmaye

    jsmaye G&G Newbie

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    Well, I did, but I just thought you were the drink-Earl-Gray-tea-in-china-saucers-with-the-pinkie-extended kind of guy...;)
     
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  13. Mike82

    Mike82 G&G Newbie

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    ouch....that presumption hurt....how could i be thought of as a fluffy person? (fluffy meaning ritsy, not like tex)....i'm from Mississippi. I CAN'T be fluffy :09:
     
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  14. GUNZABLAZIN

    GUNZABLAZIN G&G Evangelist

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    Your gonna make Grok's head hurt with all the numbers!!!!
     
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  15. Mike82

    Mike82 G&G Newbie

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    too late haha....notice how few people have replied to this compared to how many viewed? lotsa Groks on G&G it seems lawls.
     
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  16. SwedeSteve

    SwedeSteve Freedom Zealot Forum Contributor

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    Most ammunition references tend to compare calibres with only two decimal places. For instance, .25 calibre, .26 calibre, etc.
     
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  17. Mike82

    Mike82 G&G Newbie

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    that too....hence why they can be all over the place when it comes to measuring actual diameter....
     
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