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Old May 6, 2011, 08:07 PM   #1
bedbugbilly
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Question on 9mm and "9mm short" (.380)

I hope I am posting this in the correct forum as it pertains to a general handgun ammunition question. I am not that "well informed" on "modern ammunition" - (have shot black powder for over 45 years). I do shoot 38 spl and 9mm - my only exposure to 9mm has been with my Ruger SR9. I know that there is "standard" 9mm Luger - such as I use in my SR9 and there is also .380 ACP - also known as "9mm short". I have a friend who has a 9mm Springfield semi-auto and his girlfriend has a little Sig .380. One day at the range, they were shooting in the next two stalls next to mine and after they finished, he told me that he "screwed up" and mistakenly loaded "a couple" 380 ACP (from his girlfriend's ammo that had gotten mixed in with his) in his clip (for his 9mm Springfield). As foolish as he felt, he did say that they had fired in his 9mm. My question is this - I'm not that familiar with a .380 ACP cartridge or it's length - is it possible for that to occur? I'm speaking of a .380 ACP being (by mistake) loaded into a 9mm and having it fireA? I know we are talking two different calibers here when I say that a 22 short will shoot in a rifle/pistol chambered for 22 LR - also rimfire versus center fire). If a .380 ACP is a 9mm "short" and there is a 9mm "standard" such as is shot in my Ruger (9mm Luger) - can someone explain to me just what the difference is between the two besides powder charges/bullet grain size - will the chamber of a pistol that is for 9mm Luger accept a .380 ACP (9mm short) and is there a danger if one were/could be fired in a pistol chambered for 9mm Luger? BELIEVE ME - I AM NOT THINKING OF TRYING THIS . . . I am speaking in "theory" only. Or am I misinformed/ignorant in my thinking that a .380 ACP is the same as a 9mm (Luger) with the only difference is that it is a "short"? Also, I'm am not clear on how the 9mm Luger cartridge "chambers" in the barrel - i.e. since it is "rimless", does it seat at the base or at the crimp? If at the crimp, would not a 9mm "short" seat into the chamber too far for it to be fired by the firing pin? As I said, these are probably stupid questions but I hope someone out there will take the time to explain the differences between the two cartridges and how they function and why/why not a 9mm short could/couldn't be chambered in a pistol chambered for 9mm Luger and if it would or wouldn't fire. Thanks!
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Old May 6, 2011, 08:26 PM   #2
DWFan
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The 9mm Kurz Short (.380 ACP) is not a shortened 9mm Parabellum. The .380 has a case diameter of .374" above the extractor groove and is basically straightwall; the 9mm has a case diameter of .391" at the same location and tapers to .380" at the mouth. It is possible that the extractor held the .380 in place to allow the cartridge to be fired, but I would not recommend a steady diet of it.

Last edited by DWFan; May 6, 2011 at 08:32 PM.
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Old May 6, 2011, 08:29 PM   #3
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What likely happened with the 380 in the 9mm is, the rim of the case slipped under the extractor as it was stripped from the mag, and the extractor "held" the case as the firing pin hit the primer. Normally, yes, the 380 would slip into the 9mm's chamber. Most autos "headspace" on the case mouth.

The rounds are really not all that different dimensionally, so getting them mixed up isnt all that hard if you arent paying attention. The 380's case is basically just a little shorter. There are other differences, bullet shapes being somewhat obvious, but other than that, they really look pretty similar.
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Old May 6, 2011, 10:45 PM   #4
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Just to provide some additional information for your use, bedbugbilly, among widely used autoloader rounds are at least four 9mm's:
a) The 9mm Lugar or Parabellum (9x19mm)
b) The 9mm Makarov (9x18mm)
c) The 9mm "short" or .380 caliber (9x17mm)
d) The .357 Sig
NONE OF THESE ARE INTERCHANGEABLE.
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Old May 6, 2011, 11:01 PM   #5
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I have fired .380 ACP out of a 9mm Luger barrel. I have also fired it out of a .38 Super barrel. I don't recommend either, but I did it under controlled circumstances for a specific purpose, and only about two or three rounds of each.

Posts above have touched on the explanation. Allow me to expand a bit, in my usual pedantic way.

9mm Luger (Parabellum) is also known as 9x19. The "19" part refers to the length of the case. The .380 ACP, also known as 9mm Kurz ("short" in German) and 9mm Corto ("short" in Italian and Spanish) is 9x17. The "17" part, again, refers to the case length. So the .380 case is 2mm shorter than the 9mm Luger case -- that's .0787 inches. .38 Super (a 1911 caliber) is longer than both, but all three take the same diameter bullet. Typically, though, .380 also uses a lighter bullet. The "standard" bullet weights for 9mm Luger are 115-grain, 124-grain, and 147-grain. For .380, the bullet weights are typically in the 80 to 90 grain range.

As noted, the outside diameter of the .380 case is slightly smaller than the 9mm Luger -- but only very slightly smaller. The cases are close enough in diameter that in most pistols the extractor will grab the rim and hold the cartridge well enough for the firing pin to set off the primer.

But ... because the .380 case is smaller in diameter, it doesn't expand well enough/far enough to get a good seal. There's a bit of blowback around the case, and the fired cases are probably expanded beyond where I would feel safe about resizing them back to .380 dimensions for reloading.

So, that's a lengthy way of saying, "Yes, it could have happened." As noted, it's not a great idea to make a practice of it, but it's not likely to blow up a gun. More likely is that a pistol set up for 9mm Luger may not cycle on a .380 due to the combination of lower power, and gas leakage back around the case in the chamber.
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Old May 7, 2011, 08:21 AM   #6
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A big "thank you" to you all for all of the great information and explanations - you've not only educated me . . . you've cleared up my thinking on it as well! I was thinking about it after I posted my query and it crossed my mind that the extractor may have gripped the rim, holding it so that the fireing pin would set the primer off. With your explanations of the cartridge dimensions, I can see how he may have taken a "quick look" at the cartridges as he was loading his magazine and not noticed the difference. A good lesson to him (and all of us) to keep our various cartridge sizes separated. While it is something that I would never try or do - I appreciate very much all of the information that has been provided to "set me straight" on the questions and thoughts I had on what happened at the range that day. I knew that I could get the answers here and I thank you all for the great information and "educating" me on the 9mm cartridges.
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Old May 7, 2011, 10:10 AM   #7
Aguila Blanca
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To round out your newly-acquired knowledge, Google 9x18 ("9mm Makarov"), 9mm Largo, and 9x23. There are a LOT of "9mm" cartridges out there, and they very definitely do NOT interchange, despite all starting with "9."
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Old May 7, 2011, 10:41 AM   #8
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To possibly confuse you more, there is about zero danger that anybody would put a .357 SIG in a 9mm pistol, as the .357 SIG uses a necked down .40 case.

There is a hazard that one could put a .357 SIG in a .40 pistol. This is especially true as many people have guns with interchangeable .357 and .40 barrels, and both rounds fit into and use the same magazines.
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Old May 7, 2011, 11:05 AM   #9
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In some pistols chambered for the 9mm Luger (the official SAAMI name in the US for the 9mm Parabellum), the .380 ACP will fire without being held by the extractor because the firing pin reaches out well beyond the breech face. The case backs up and may expand or split, but there is seldom any damage to the gun or the shooter.

One problem which is rarely addressed is the situation where an entire "wrong" cartrige can move into the barrel far enough for a "right" cartridge to be chambered behind it and fired. That usually happens when the "wrong" cartridge is the top round in the magazine, and when the slide is manually cycled, moves far enough in that the gun misfires. Thinking a round failed to chamber, the shooter again racks the slide, chambering a "right" round, and fires. Depending on where the "wrong" cartridge is in the barrel, the result can be nothing more than high pressure, or the barrel can be bulged or split and the gun destroyed.

This can happen in the case of a 9mm Luger in a .40 S&W barrel or a .40 S&W in a .45 ACP or .45 GAP barrel.

Jim
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Old May 8, 2011, 12:25 AM   #10
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I have never tried to shoot a 380 in a 9mm but I can see how it might happen.

I did under a controlled situation shoot some 380acp in a 9x18 Makarov. As the 9x18 is hard to find in some places I wanted to see if you could use 380 in a pinch. It worked and shot fairly accurate also. The 380 case was bulged and I would not have reloaded them. Not much different than some 380 cases I get from class III shooters.

A gun chambered in 9x18 would make a better self-defense round than the 380. But sadly ammo is sometimes hard to find. I have bought and sold and shot several of the European imports that were on the market 10 years ago. I found them to be guns of good value. Quality versus price. Many were under $200.00.
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Old May 8, 2011, 10:15 AM   #11
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Saw a guy bring a bag full of gun show 380 reloads to the range to shoot in a Browning BDM.

Didn't work.
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Old May 8, 2011, 01:13 PM   #12
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.380 is a caliber I avoid purchasing, for the topic reason stated here.

I wouldn't want to find out the hard way if my 9mm pistols could do it.

I go out of my way to avoid purchasing any caliber which could be

easily mixed up with anything I already own.

Again not what TO DO, just what I do...
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Old May 8, 2011, 03:17 PM   #13
lee n. field
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Quote:
As foolish as he felt, he did say that they had fired in his 9mm. My question is this - I'm not that familiar with a .380 ACP cartridge or it's length - is it possible for that to occur? I'm speaking of a .380 ACP being (by mistake) loaded into a 9mm and having it fireA?
Conceivable. Looking at the case dimensions, the .380 is a little thinner overall (.374 vs. .391 at the base), and less tapered than 9mm. The extractor might be holding it in place (loosely), keeping the firing pin strike from driving it deeper into the chamber.

Yeah, I could see it happening. Might very well not successfully cycle the slide, though.

Quote:
There is a hazard that one could put a .357 SIG in a .40 pistol. This is especially true as many people have guns with interchangeable .357 and .40 barrels, and both rounds fit into and use the same magazines.
Somewhere around here I have a piece of range pickup brass, a .357 Sig case blown completely straight.

Quote:
If a .380 ACP is a 9mm "short" and there is a 9mm "standard" such as is shot in my Ruger (9mm Luger)
There are a whole raft load of different "9mm" cartridges. 9x19, 9mm Luger, 9mm Parabellum, are all the same, and are probably what people mean when they say "nine mil". 9x17 is .380. "9mm Makarov" is an old commie 9x18 cartridge, a hair fatter (.365) than those others. Those are just the common one's you'll run into.
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Old May 8, 2011, 05:26 PM   #14
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Quote:
Somewhere around here I have a piece of range pickup brass, a .357 Sig case blown completely straight.
Somewhere around here, I have a couple of pieces of .40 brass that look like a 357SIG.

Weird stuff happens when you dont pay attention. I reloaded a few pieces of .40 brass into 357SIG without ever noticing. They shoty fine too.


As for strange things being shot out wrong guns, my buddys kid got a 30-30 loaded into his dads 35Remington, and got it to fire. He now has a piece of brass that has a 30-30 Winchester rim and headstamp, and looks like a 35 Remington everywhere else.

Lesson learned there was, dont keep similar guns and there accessories and ammo on the same bench, especially when inexperienced people are around and shooting too.
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Old May 8, 2011, 06:57 PM   #15
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Quote:
Depending on where the "wrong" cartridge is in the barrel, the result can be nothing more than high pressure, or the barrel can be bulged or split and the gun destroyed.
9mm will fire in a pistol chambered for .40. The case mouth bells out, and of course, the bullet keyholes something awful. Despite that, I see people do it about twice a month at the range.

Lesson #1: when you're shooting multiple guns in a session, keep the ammunition from getting mixed up.

In another case, I saw a guy bulge the barrel on a Baer 1911. We were shooting outdoors, and he dropped a round in the grass while loading his magazine. He missed the round he meant to pick up, and instead picked up and loaded a round of .40. The barrel looked just like a squib had been followed by a live round. The locking lugs in the slide were also chipped.

Lesson #2: if you drop a cartridge, let it go. It's not worth wrecking the gun.

While we're talking about the whole confusion of 9mm cartridge naming, let us take a moment to remember the 9mm Glisenti, 9mm Police, 9mm Bergmann, 9mm Browning Long, and 9mm Steyr.
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Old May 8, 2011, 08:15 PM   #16
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You missed the 9x23Winchester and the weirdo of the lot, the 9x25Dillion (10mm case necked down to 9mm and yeah, it's a beast and can spank the 357Mag - it was meant to maximize what you could do with a single-stack 1911 during the Dark Days of the 10rd mag limit.
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Old May 8, 2011, 09:24 PM   #17
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A comprehensive thread with a lot of good info...
One thing I haven't seen mentioned yet is pressure.

The .380 runs at a lower chamber pressure than the 9mm is designed to run at. The .380 runs at 21,500 PSI max while the 9mm is designed around 35,000 PSI.

A smaller case, as long as the bullet is the same bore diameter or smaller, isn't what you should put in to your pistol and it won't do your extractor any favors... but it shouldn't be specifically dangerous or threatening. (unless, as Jim Keenan pointed out, it ends up lodged in the barrel and a proper round is fired behind it)

The last example given of a .40 S&W in a 1911 chambered in .45 cal is bad, because the .40 cal is a high pressure round (35,000 PSI) in a pistol designed to run at 21,000 PSI. Not at all good! But in theory... the .40 cal round shouldn't have even gotten to a full 35,000 PSI because that pressure wasn't properly contained. Given the damage that resulted... not so good!

As a side example of what I'm saying... rifle shooters who play with wildcats do their share of fire forming. A wildcat to a rifle guy is a caliber (or more accurately, a chambering) that is not loaded by any factory ammo source. Instead, wildcatters must either buy brass that is formed to the spec of the cartridge and handload themselves, or they must form their own brass before they can even handload it.

Often enough, they will "create" the brass they need by fire forming, or shooting the parent case which is smaller than their chamber in their rifle. Many will make reduced loads with a faster powder to "blow out" the cartridge case to fit the chamber -- they do it with chamber pressure.
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