At least you didn't put a more volatile liquid down the tube and try to fire it. A really light oil or cleaning fluid could cause a
diesel effect and detonate when a gun is fired. I realize the power level isn't the same but this was a problem for guys maintaining spring airguns. There have been documented cases of severe velocities ( and damage) from spring airguns that were lubed or cleaned with improper products or with proper materials but incompletely.(Although I looked this effect up just now and find there is actually a type of RWS made air gun that is made to capitalize of a degree of diesel effect) It(damage) nearly happened to me once after an incomplete cleaning of a Wischo CM air pistol; I got quite the bang and the .177 pellet shot with great force but inaccurately...

Jerry