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.
Thank you for clearing that up. I wasn’t sure if I was hearing wrong, or some MSM idiot was claiming that the assailant used a ship’s cannon off the Iowa to kill the local Republican, which wouldn’t surprise me.