In all seriousness, Karl is a cool guy and he's got a good sense of humor. This is epic trolling right here, that's what that is.
In case you aren't familiar with InRangeTV, they perform a lot of mud tests on guns. The joke is about a gun getting the bucket/hose if it won't function properly, a play on the scene from Silence of the Lambs.
It's actually a catchy song once you get over the association with Ted Levine's disturbing tuck scene in the film.