This may sound like a very basic question, and for that I apologize. But, what is the difference between 380 ACP and 380 Auto? I've seen this kind of designation on other calibers also and have often wondered. I guess it's time to embarrass myself and ask.
Valid question! The acp is the original designation. It stands for automatic Colt pistol. From way back in the days of John Browning when Colt was the premier pistol manufacturer. So when Browning invented the .25, the .32, the .380, and the .45, the Colt company was one of the main sponsors and makers of pistols in those calibers. Naturally, the ammo was named that way.
So acp has hung on but we just call it auto for short.
Now 9mm is a little different having started in Europe for the Luger pistol. So it's often referred to a 9mm Luger.
Thanks to both of you. Is it the same situation with 9mm? I've seen 9X18 mm Ultra, 9mm Luger, 9X21 mm, 9X23 mm Winchester and 9 mm shotshell. Are they all usable in my PM9 and S&W M&P 9C? I've been using the 9 mm Luger and it's been doing fine? Sorry for the lack of knowledge here, but I just started getting involved with handguns after last November.
Actually there are 3 "9mm" cartridges, 9x19 which is the std. 9mm Luger, 9x18 which is known as the Makarov pistol cartridge, and our 9x17 .380acp cartridge.
A good place to get data on lots of ammunition details is this link....
For a standard American 9mm pistol what you want is the 9mm Luger. The 9x17 .380acp round might fit in a 9mm pistol but would be very dangerous to try so don't try it. It could damage the gun and possible you. The Makarov round probably won't fit as it's a bit larger diameter case. But some people have tried and it again would be very dangerous.