Pardon my ignorance. But my first pistol that I owned legally was a .38 caliber snub-nosed S&W revolver. .380 is a different bore than .38? My algebra teacher would have kittens. 380 would be 380 inches. I don’t know if artillery comes that big.
You are correct. A.380 is 380 thousandths of an inch in diameter. Technically, your .38 was about .357 inches. Calibers get odd labels, sometimes. A .270 Winchester fires a projectile of .277 inch diameter.