Many moons ago, I started telling anybody I was handing a firearm to that it was 'Loaded'. They all handle it with respect until they know it's clear. Range officers asking to check my weapon before qualifying get jumpy, but better safe than sorry.
Reason I started that is:
Once, I may have been 15-16, I handed over a Browning Hi-Power and said the chamber was unloaded. My mentor pulled the slide back and pointed it at the floor and fired it before I could react! He said he pulled the trigger about the same time his brain said "That shouldn't have gone forward", talking about the slide.
At least his wife only jumped a little and kept cooking!