Hey Folks, I too can be ignorant. About 25 years ago, my Grampa died, leaving us various rifles and 2 handguns. I took the 2 handguns out in the woods to shoot. One was a little 7.65 auto. I knew that 7.65 translated to .32 acp, and had bought 32acp to feed it. The other was an old S&W model 10. I just brought (from the drawer that it was in) several boxes of 38 spl. The barrel was clearly marked 38 S&W. What I didn't know, was that 38S&W and 38 spl ARE NOT interchangable. After shooting a couple of rounds and having my hands peppered with lead shavings (and astoundingly lousy accuracy), I went home, looked in an old reloading manual, and discovered that they are different caliber rounds. ...And I considered myself a "gun guy". Fortunately, neither the gun nor myself was hurt. Sure felt stupid though. Glad I was shooting lead and not jacketed.
By the way, properly loaded, that old Mod 10 really is a tackdriver.