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Thread: 40 cal v 10mm

  1. #1
    Shooting at the big range in heaven. 1952-2009 The Village Idiot's Avatar
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    Default 40 cal v 10mm

    This may have been covered before but..

    If 40 cal = 10.16mm and 10mm = 39.37 cal, what is the difference between the two and why do people seem to prefer the 10mm over the 40 caliber? Is it in the loading?

    Thanks,

    Ed
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    Instructor Mike-Mike's Avatar
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    The length of the cartridge. It's like a .38 and .357 mag.

    They are the same caliber one just the ability to carry more powder and higher pressures.
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    Shooting at the big range in heaven. 1952-2009 The Village Idiot's Avatar
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    Makes sense.

    Thanks,

    Ed
    EdH



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    NES Member jar's Avatar
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    The 40 is a descendant of 10mm. The 10mm auto cartridge was adopted by the FBI after the 1986 Miami shootout. The FBI decided that the recoil of full power 10mm loads was too much for many agents, so they specified a reduced load. Smith and Wesson realized that with the FBI load they didn't need the full case capacity of 10mm. They created the 40 S&W to allow them to build pistols for the FBI loading on the same frame size as 9mm, and now the 40 is far more popular.

  5. #5
    Moderator M1911's Avatar
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    The shorter .40 cartridge allows for a smaller grip circumference. 10mm allows for a more powerful load if desired.

  6. #6

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    Quote Originally Posted by The Village Idiot View Post
    ...what is the difference between the two and why do people seem to prefer the 10mm over the 40 caliber? Is it in the loading?
    It's all about the load. The bullets are typically the same, except for the 200 grainers, which typically are only found in 10mm Auto loadings. 10mm Auto has a longer
    case, usually thicker brass, and a large pistol primer for ignition.

    The key technical difference is that .40 S+W "roofs out" pretty quickly- there's literally not a whole hell of a lot of headroom in loading .40 S+W, especially with 180 grain bullets. In .40 S+W said bullet might be cruising around 1050 fps tops at pressure max. In 10mm auto that same bullet can be going well northward of 1200 FPS!!!

    Basically, think of .40 S+W as an intentionally crippled 10mm. It's not that it's a completely terrible cartridge, but it's WAY less versatile than 10mm Auto is, and the maximum
    power capability of the 10mm is easily an order or so of magnitude greater than .40 S+W.

    -Mike
    Last edited by drgrant; 08-17-2008 at 04:56 PM.

  7. #7
    Shooting at the big range in heaven. 1952-2009 The Village Idiot's Avatar
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    I appreciate the answers to my questions. There is a wealth of knowledge to be tapped here on NES. A couple of goofy shits like myself, but a lot of knowledge.

    Thanks all,

    Ed
    EdH



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    What does not kill us makes us stronger - what does kill us makes us, uh, dead.

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  8. #8
    NES Member vellnueve's Avatar
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    The bullet diameter is the same. The 40 S&W is just a shortened 10mm case.
    Disclaimer: I am not a lawyer and thus any interpretation or statements about the law that I might make should be taken with a grain of salt and mixed with your own legal research as well as advice from actual legal counsel. I cannot be held responsible if you find yourself somebody's "friend" in federal, state, or local prison should you act on my opinions on the law. My interpretations of the law will generally be on the conservative side.

  9. #9

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    Quote Originally Posted by vellnueve View Post
    The bullet diameter is the same. The 40 S&W is just a shortened 10mm case.
    True on the former, but not entirely so on the latter. The case head area of the 10mm has a slightly thicker web and it also takes a large pistol primer instead of a small one. Of course I'm being pedantic here, but this is one of the main differences between the two, and it also contributes overall to the difference in capability between the cartridges.

    -Mike

  10. #10
    NES Member vellnueve's Avatar
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    -1 for myself
    Disclaimer: I am not a lawyer and thus any interpretation or statements about the law that I might make should be taken with a grain of salt and mixed with your own legal research as well as advice from actual legal counsel. I cannot be held responsible if you find yourself somebody's "friend" in federal, state, or local prison should you act on my opinions on the law. My interpretations of the law will generally be on the conservative side.

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