Only reason l can see is if its run unsuppressed it would do less hearing damage if used in the home for self defence.

Being pragmatic: why not just build your pistol caliber carbine chambered in 9mm Luger which exhibits barely noticeable extra recoil, produces increased muzzle velocity, and costs less (for ammunition)?

Just Saying (OG),

Short version (because comments with more than 10 words or more than one comment every 30 minutes apparently are automatically hidden/deleted):

The shorter casing of .380 ACP (compared to 9mm Luger) means reduced muzzle velocity and accuracy as well as a much higher probability of failed extraction and light (or no) primer strikes.

Just Sayin (OG),

I replied to your comment and explained why it is probably a bad idea to try and shoot .380 ACP out of firearms chambered for 9mm Luger.

Unsurprisingly, this site immediately made that comment vanish for absolutely no good reason whatsoever–as it does so often.

Just Sayin (OG),

My somewhat educated guess as to why you should not just load .380 ACP into a pistol caliber carbine chambered in 9mm Luger is due to the dimensions (length specifically) of the chamber and the 2mm difference in the length of the casing between .380 ACP and 9mm Luger.

A chamber for 9mm Luger is just barely long enough for 9mm Luger cartridges which make a sort-of tight seal as the chamber transitions into the bore of the barrel. That maximizes both accuracy and muzzle velocity. (The less distance that a bullet has to “jump” out of the chamber into the barrel translates to better alignment of the bullet’s axis with the barrel’s bore axis and hence better accuracy. Similarly, the less distance that a bullet has to “jump” out of the chamber into the barrel also translates to trapping more gases and increasing muzzle velocity.)

There could also be significant trouble with extraction. The extractor for a 9mm Luger chamber reaches just far enough past the rim of a fully seated 9mm Luger casing in the chamber to grab it and yank it. Since a .380 ACP casing is 2mm shorter than a 9mm Luger casing, that .380 ACP casing could move forward in the chamber and the extractor may not reach forward far enough to grab the rim of the shorter .380 ACP casing.

Another potential problem is primer strikes. The firing pin for 9mm Luger cartridges only moves forward far enough to ignite the primer when a 9mm Luger cartridge is fully seated in the chamber with the primer-end of the casing extending backwards some defined distance. However, .380 ACP cartridges are shorter and may seat fully forward in the chamber which means the firing ping may not strike the primer at all since the .380 ACP casing is 2mm shorter.

All of this simply illustrates how caliber designations define more than just bullet diameter–they also define cartridge lengths and casing profiles (e.g. straight-wall versus bottle-neck casings).

Just Sayin (OG),

My somewhat educated guess as to why you should not just load .380 ACP into a pistol caliber carbine chambered in 9mm Luger is due to the dimensions (length specifically) of the chamber and the 2mm difference in the length of the casing between .380 ACP and 9mm Luger.

A chamber for 9mm Luger is just barely long enough for 9mm Luger cartridges which make a sort-of tight seal as the chamber transitions into the bore of the barrel. That maximizes both accuracy and muzzle velocity. (The less distance that a bullet has to “jump” out of the chamber into the barrel translates to better alignment of the bullet’s axis with the barrel’s bore axis and hence better accuracy. Similarly, the less distance that a bullet has to “jump” out of the chamber into the barrel also translates to trapping more gases and increasing muzzle velocity.)

There could also be significant trouble with extraction. The extractor for a 9mm Luger chamber reaches just far enough past the rim of a fully seated 9mm Luger casing in the chamber to grab it and yank it. Since a .380 ACP casing is 2mm shorter than a 9mm Luger casing, that .380 ACP casing could move forward in the chamber and the extractor may not reach forward far enough to grab the rim of the shorter .380 ACP casing.

Another potential problem is primer strikes. The firing pin for 9mm Luger cartridges only moves forward far enough to ignite the primer when a 9mm Luger cartridge is fully seated in the chamber with the primer-end of the casing extending backwards some defined distance. However, .380 ACP cartridges are shorter and may seat fully forward in the chamber which means the firing ping may not strike the primer at all since the .380 ACP casing is 2mm shorter.

All of this simply illustrates how caliber designations define more than just bullet diameter–they also define cartridge lengths and casing profiles (e.g. straight-wall versus bottle-neck casings).

“You overlook the site’s spelling errors, and we’ll overlook your grammar & diction shortcomings.”

You typed the words right out of my fingers! Lol.

Make you a deal…

You overlook the site’s spelling errors, and we’ll overlook your grammar & diction shortcomings.

(Oh, and I decided to post a comment because this is the first page in three days that doesn’t have .40’s energy all over it and actually left room for the rest of us)

I use a wire wrapped base ball bat for zombies.