Shoot .40 S&W in a 10mm?

Discussion in 'Glock Forum' started by larryjbjr, Jun 27, 2016.

  1. larryjbjr

    larryjbjr New Member

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    Is there any reason you couldn't just shoot .40SW in a G29 ?

    I know you can shoot .38 special in a .357 mag, even though the cartridge is shorter, so why couldn't I shoot .40S&W in a 10mm?

    I assume there is a reason, but I want to understand what it is. So please be nice. :)
     
  2. i gonna guess and say the .40 can't headspace in a 10mm barrel cause it's shorter than the 10mm. rimless cartridges headspace on the case mouth.

    this is actually a very good question and probably of interest to a lot of people.
     

  3. gmcttr

    gmcttr New Member

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    .38 and .357 mag are supported/headspaced by the larger diameter case rim.

    I know nothing about .40S&W or 10mm except that they are supported/headspaced by the case mouth. Even if there were no other concerns, the shorter case would be able to move too far forward in the chamber (if it escaped the extractor) causing inconsistent fail-to-fires as happens when a .380acp is chambered in a 9mm.
     
  4. norseman10

    norseman10 New Member

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    From my research... the consensus from those who have actually tried it is that it works fine. The extractor will hold the round in place. But, it will be weaker than it otherwise would be, due to gasses escaping from the excessive headspace. That being said - I personally dropped $100 for a .40 conversion barrel to put in my 20 and it works great.
     
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  5. SixG17s

    SixG17s Well-Known Member Supporter

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    Some of the guys in USPSA who run G20's shoot 40S&W load long. The extractor will hang on to the case and it will run fine.

    Not the same as a .380acp vs 9mm. The base and rim of the 9mm are .391" vs .374 for the .380. Also the neck is .007" smaller on the .380 and it's a straight wall case. That's why it blows smoke in a 9mm chamber and can't hit anything. That's not the same as the 10mm and 404S&W which are the same dimensions except for length.
     
    Last edited: Jun 27, 2016
  6. gmcttr

    gmcttr New Member

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    Good to know, thanks.

    At least I got one thing right....

    :laugh:
     
  7. 40caljim

    40caljim Active Member Supporter

    No, no, and no. Shooting 40 in a 10mm may damage the chamber. One of the 10 safety rules of firearms is always use correct ammunition. Don't think about, do 't even discuss it, and more important DON'T DO IT.
     
  8. Lucian_253

    Lucian_253 Well-Known Member Supporter

    So in summary. Can you shoot .40 S&W out of a Glock 20...yes. Should you shoot .40 S&W out of a Glock 20... No No & No.
     
  9. larryjbjr

    larryjbjr New Member

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    Thanks to all for the info.

    Doesn't sound like something I want to try.
     
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  10. G29er

    G29er New Member

    It'll do in a pinch in case of emergency like running out of 10mm ammo but have 40sw ammo.

    I've researched it and lots said no problem but accuracy will suffer. Also said that no damage was done to the chambers. I've read otherwise so I guess it depends on the gun, is it good or cheap.
     
  11. rbbeers

    rbbeers Well-Known Member Lifetime Supporting Member

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    Given that the 40 S&W is simply a short 10 mm Auto (please refer to the SAAMI Standard below), as long as the 40 S&W cartridge doesn't 'jump' the extractor and fail to fire, it's the same as shooting a 38 Special cartridge in a 357 Magnum revolver... actually, it's like shooting a 357 Magnum cartridge in a 357 Magnum revolver, since neither the 40 in the 10 nor the 357 headspace on the case mouth.

    ANSI/SAAMI Z299.3 - Centerfire Pistol & Revolver - 2015
    http://www.saami.org/specifications_and_information/publications/download/205.pdf

    Best regards,

    Bob :)
     
    Last edited: Jun 28, 2016
  12. G29er

    G29er New Member

    The difference between the 10mm and the 40sw casing is 3.6mm in length. That's 0.142" Not a whole lot.

    It is similar to shooting 38sp in a 357 but not the same. The revolver has a forcing cone but not the semi-auto pistol.
     
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  13. rbbeers

    rbbeers Well-Known Member Lifetime Supporting Member

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    As long as the 40 S&W cartridge headspaces on the extractor and the primer ignites... sending the bullet on its way... everything else is semantics and inconsequential.

    It's that simple.

    Bob
     
  14. rbbeers

    rbbeers Well-Known Member Lifetime Supporting Member

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    Anecdotal comments from Calguns.net...

    can you shoot 40 S&W in a 10mm gun?
    http://www.calguns.net/calgunforum/showthread.php?t=135850

    The highlighted comments reflect my personal position as well.

    Although I've never read of a 'kaboom' shooting a 40 S&W cartridge in a 10 mm Auto pistol, since the primer cup is a few thousandths of an inch shorter than the difference in case lengths, in theory, however unlikely, pressure 'blowback' seems possible... and should be avoided. (I truly don't understand how that would happen, but I'll let someone else find out.)

    Best regards,

    Bob :)
     
    Last edited: Jun 28, 2016
  15. G29er

    G29er New Member

    Since I knew I can shoot 40s in my 10mm in a pinch I went ahead and got a LW 40sw barrel for it.
     
  16. SixG17s

    SixG17s Well-Known Member Supporter

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    I've seen the dummies shoot 9mm our of 40S&Ws. Doesn't hurt the gun, smokes a little, not accurate at all, and makes a really weird looking case bulge...

    I know guys that run 220 grain 40S&W to 10mm OAL all the time. Doesn't give as much length for the bullet to hang on to, but it works fine.

    Here is a little blip from Benos

    http://www.brianenos.com/forums/index.php?showtopic=125395
     
  17. SixG17s

    SixG17s Well-Known Member Supporter

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    Your'e not going to KaBoom a 10mm with a 40S&W. That is caused by excessive bullet setback, not excess head space. A setback of only .100" in a 9mm will double the pressure. And you won't erode the chamber either, not at 1,000 fps. Yea, at 3,200 fps in a rifle. Almost forgot, it was some time ago, I carried a G20 for several years, and ran at least 4-5 cases of 40S&W ammo thru it for qualifications and practice. It works fine, not as accurate as 10mm at 50 yards, but at 15 yards, no difference.
     
    Last edited: Jun 28, 2016
  18. floridave

    floridave New Member

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    Old thread and several differing opinions, but I’ll add a data point, that I’ve shot thousands of 40 cal reloads out of my 10mm G20 with its stock barrel. No problems for me at all. I have multiple 40’s, cheap brass and keep lots of that ammo. No big deal leaving some brass at the range, 10mm brass I’m more careful about trying to hang on to. When I shoot actual 10mm, the loads are heavier and used in both the Glock and 1911.
     
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  19. Overkill338

    Overkill338 Proponet of High Velocity Supporter

    How would gases escape? The case is the same diameter as a 10mm. Is there a vent in the front of the chamber that I don't know about? My 29 shoots 40's just fine and they chronoed as they should. Power and accuracy are just fine, and the guns have no issues at all. I've run 1000+ 40's through my 29 and no trouble what so ever. Lots of people do it.

    Damn it, I always fall for the old threads lol

    I don't tell anyone to shoot 40's from their 10's. I just tell them it hasn't hurt mine yet.
     
  20. SixG17s

    SixG17s Well-Known Member Supporter

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    Gas escapes because a 40 is .100" shorter in the chamber