9mm vs. .380

[SomedumGuy]

This isn't to debate the merits or shortcomings of either round ( you're welcome to, I don't really care ), but to answer a question:
I have a Walther PPK-s, Cold War, Made in W Germany stamped on the barrel. Also stamped there is 9mm, but it only accepts .380. A 9mm  (ACP) slug is too large diameter to fit through the barrel. Does the European measurement designate a different size? Why does it say 9mm when it isn't?

[Timothy]

.380 ACP or 9mm Corto or Kurz, Browning and Short are all the same and are exactly the same diameter bullet as 9mm Luger!  They .380 bullet is lighter and the case is shorter than 9mm Luger.  .380 or 9mm Short is 17mm case, 9mm Luger is 19mm case length.  You cannot shoot 9mm Luger in a PPK or PPKs!

No bullet will travel freely down a barrel without being fired.  If you're trying to fit a 9mm Luger into the chamber it won't fit because it's too long for the chamber by approximately 2mm.  (over 1/16")

[Big Frank]

What he said. ^ Also I believe the head of the 9mm Luger case is just a hair wider.

[Timothy]

What he said. ^ Also I believe the head of the 9mm Luger case is just a hair wider.

Is that due to the increased case wall thickness due to higher pressures, Frank?

[Big Frank]

The 9mm rim is tapered about .012" wider than the case mouth and the .380 is basically straight at .001" of taper. My guess is that the taper is to make it feed better.

[Sponsor]

[alfsauve]

There are three rounds to consider here.

9x19 or 9mm Luger - bullet .355, Pressure ~35,000
9x18 or 9mm Makarov - bullet .364, Pressure ~24,000
9x17 or .380 or 9mm Short...  - buller .355  ~21,000

The Markarov is 1mm short than the 9mm Luger but other dimensions are similar EXCEPT it uses bullet that are .364 in diameter.   It is a lower pressure round.  With a good extractor you can fire the 9x18 in a 9mm Luger gun.  No particular problem. Wouldn't depend on it working every time though.  I've on rare occasion found a case in my range sweepings and load it with .355 bullets and it has worked fine.  A testimony to Glock's ability to digest most any ammo. 

The .380, contrary to what some people think isn't just a shorter 9mm.  It is smaller dimensionaly in all respects to the 9mm Luger including the case wall thickness.  That allows it to use the same size bullet.  I've tried to chamber a .380 in a 9mm but it is too small for the extractor to hold in place.  Not that it couldn't happen.  The risk would be if you did manage to fire it. is that the case would not seal the chamber and you'd get blow back.