That's possible - when loading a round into the chamber of an auto pistol
with a finger on the trigger
A
modern gun will fire when it's wet, as long as the inside of the cartridge is dry. It doesn't matter if the gun or the outside of the ammo is wet. Unless the ammo has been under water for many years, it will fire because the primer (which ignites the powder) is very tightly fitted into the primer pocket at the back & the front of the case (shell) is tightly crimped around the bullet. Additionally, to prevent water (or anything else) from contaminating the ammo, most manufacturers use a lacquer sealant around the primer pocket and asphalt at the front of the cartridge. In fact, manufacturers frequently demonstrate how reliable their guns are by dropping them into a muddy lake, then retrieving them & firing.
The primer creates a spark that travels through the flash hole & ignites the powder, which creates the gases that force the bullet out. If there is no water inside the cartridge, it will fire. You can see that it is very unlikely that any water would get in, since everything is sealed.
There was a time in the past when getting a gun wet could render it temporarily inoperable, but that was back in the days of black powder and flintlock guns. The gunpowder was not contained inside a watertight cartridge in those days and if the gun got wet the powder would get wet, and wet gunpowder simply will not ignite."
Here is someone testing the reliability of a wet gun - similar to U.S. Army tests: (skip to 2:52 if you just want to see the water test)
