Quote Originally Posted by Johnny P View Post
If a rifle has fired blanks you only have a short window to get it out before the blackpowder residue starts attracting moisture and rusting the bore.
IIRC military blanks are a small charge of fast burning smokeless propellant.

I do recall owning some starter pistol blanks which were black powder based. The smoke being a virtue in that case because it gives a visual indication. And yes 100% true about cleaning.