What movie guns can be fired with no blank adaptor?

[joffeloff]

If you have one of the few handguns that use a gas impingement system rather than recoil (P7, Desert Eagle, don't know what else) it's still going to need a projectile in order to function. The only reason the impingement works as well as it does is because it is actuated between the points where the bullet passes the port of the gas tube and when it exits the muzzle at which point any pressure subsides. Without a projectile you won't get enough pressure in the muzzle to cycle anything no matter how much you adjust.

At least, that's 'common sense' from my end.. Can't say I've ever worked with prop blanks so I can't say for sure.