I have to tell my story before Bob tells it for me.
I had a 223 round get mixed into my ammo pile. In a haste of reloading it ended up in my mag on the dash between barricades drill.
I've fucked this up before at C4, but this time it was a little different. Somebitch fired, and even Got Some (but it sounded a felt like a suppressed shot to me). No damage to the gun, just my dignity.