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Thread: JCN has all kinds of bad ideas: 380ACP out of a J-frame

  1. #21
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    Quote Originally Posted by Trigger View Post
    I wouldn’t. The .380 (9x18mm, 9mm Kurz) is a tapered case, the .38/.357 is a straight walled case. In your photo below, you see the chambers cut into the cylinder, with the front end of the cylinder cut to size smaller than the chamber, but large enough to lead to the forcing cone of the barrel. When you fire the .380 round, there is no way to hold the tapered case concentric with the bore of the cylinder, and the bullets will likely bang into the end of the cylinder and the forcing cone unpredictably, potentially causing pressure spikes. Plus you have the difference in case length, leading to fouling buildup in front of the 380 case mouth, which will make it difficult to shoot the longer .38/357 later due to the fouling buildup.

    Attachment 70521

    That’s with the moon clip fitting.
    I don’t know about the rest of it, and I’m waiting to see what happens, but you are mistaken about the .380 being a tapered case. 9x19 Parabellum is tapered with .394 case head and .380 case mouth, while the .380 is .374 case head, .373 case mouth. .38 Special has .379 as the spec for the case mouth, so there will be room for the .380 case to expand in the chamber. I rather imagine that it will. I doubt the slightly smaller bullet passing through the rest of the chamber after it leaves the case is going to damage anything, or we’d already see that after the last ~100 years of shooting .38 Specials through .357 chambers.

  2. #22
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    Quote Originally Posted by Trigger View Post
    I wouldn’t. The .380 (9x18mm, 9mm Kurz)

    That’s with the moon clip fitting.
    Good points! But 9x17... 9x18 is Makarov which doesn’t fit because of the wider base of the cartridge.

    Will be interesting to see where the accuracy shakes out at!

  3. #23
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    Quote Originally Posted by JCN View Post
    Good points! But 9x17... 9x18 is Makarov which doesn’t fit because of the wider base of the cartridge.

    Will be interesting to see where the accuracy shakes out at!
    I think that the accuracy will not be terrible, because we have been shooting 9 mm Parabellum through .357 Ruger Blackhawk barrels in the convertibles for generations, and while the accuracy isn’t as good typically as the .357‘s or .38s, it isn’t usually terrible. .380 and 9mm Parabellum bullets are both nominally .355, so it should be comparable.

  4. #24
    Revolvers Revolvers 1911s Stephanie B's Avatar
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    It might work. It might be a “Hold my beer and all y’all watch this” exercise.
    If we have to march off into the next world, let us walk there on the bodies of our enemies.

  5. #25
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    Quote Originally Posted by Duelist View Post
    I think that the accuracy will not be terrible, because we have been shooting 9 mm Parabellum through .357 Ruger Blackhawk barrels in the convertibles for generations, and while the accuracy isn’t as good typically as the .357‘s or .38s, it isn’t usually terrible. .380 and 9mm Parabellum bullets are both nominally .355, so it should be comparable.
    I think he’s concerned that due to the case mouth being not centered the bullet might hit the cone/barrel a little crooked or wobbly. I’m not sure how much wobble and slop will matter.

    I definitely think 380 out of a 9mm chamber isn’t going to work because of the floating case but the 380 fits decently snug/centered I think.

    We shall see! This thought experiment might only last one round, lol.

  6. #26
    The Nostomaniac 03RN's Avatar
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    Quote Originally Posted by Stephanie B View Post
    “Hold my beer and all y’all watch this”.
    That's my middle name

  7. #27
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    RESULTS: underwhelming



    It worked and was super pleasant and mild to shoot!

    But velocities and accuracy were meh, as people had suspected.

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    Same ammo out of an LCP:

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    7 yards semi slow fire with the J-frame: 380 versus 38 special

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    So while you could do it and it’s very mild to shoot, it has limited SD application.

    @Trigger and @03RN win for the most accurate predictions!

  8. #28
    Glad it worked out safely, even if it was underwhelming.

    Thanks to all for correcting my errors, I need to verify better before posting! I will say 380 is pain to deal with then it gets mixed into my 9mm cases.
    "Government is not reason, it is not eloquence, it is force; like fire, a troublesome servant and a fearful master"

  9. #29
    Site Supporter jandbj's Avatar
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    JCN has all the cool toys.

    I’ve lusted after an LCP Custom since they stopped making them. Wish they’d put those sights on the LCP2 in .380 & .22LR! Time to hit up the Ruger suggestion box again.

  10. #30
    Member GearFondler's Avatar
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    Well this was a fun thread.

    Load it with .380 FMJ and it would still do the job if it didn't ricochet off bones.

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