It's also a safety thing. The main function is for the firearm to function properly with blanks instead of live rounds. Not all types of firearms need blank fir

It's also a safety thing. The main function is for the firearm to function properly with blanks instead of live rounds. Not all types of firearms need blank firing adapters to function properly with blanks. Edit to expand on that: Various types of autoloading firearms rely on the gas from the combustion of the powder in the round to be directed a certain way which provides the energy needed to cycle the bolt, which includes ejecting the spent round and feeding the next round. If that gas escapes out the end of the barrel then that action doesn't happen and remedial action must be performed on the rifle (in the case of an AR style rifle it means working the charging handle). With a revolver (at least mine), the cylinder is spun using the energy from squeezing the trigger so it doesn't matter if the gas escapes out the end of the barrel. I'm not sure how safe that would be to use a blank firing adapter on a revolver if there's no other way for the gas to escape.