What movie guns can be fired with no blank adaptor?
 

Wondering, is there anything that will cycle blanks without any adaptor?

Yeah, a mini gun..... :D Other than that, only manually operated guns will cycle with blanks and live rounds interchangeably.

A revolver doesn't need a blank adaptor.

A Gatling Gun probably doesn't need any adaption. Bolt guns, lever guns, anything that doesn't fire semi/full auto basically.

But NO semis can cycle blanks?

no without blank adaptors

No. Semi-autos depend on the force of the pressure and/or gas generated by the projectile exiting the muzzle to cycle. Blanks don't really have a projectile, so they don't generate enough force to cycle the actions unless the barrel is partially plugged (the blank adapter/restrictor basically serves the same function that the bullet itself would serve in normal operation).

blank guns
 

There are a couple of semi auto shotguns that will cycle without blank adaptors but the FFXhot loads must be used. They function at about 90% which is not reliable enough to take chance with during filming. This is mainly due to the inconsistant nature of shotgun blanks. Add a slight restriction and the consistancy of the burn and pressure increases.
The Milkor M32 40mm although not a true gas operated semi auto will work on a 12ga or .45-70FF load. These loads develop a pulse that will depress the spring loaded cylinder pin which lets the pre wound cylinder advance to the next position. It fires as fast as you can pull the trigger.

4570guy

What about autos that can be adjusted for gas pressures? Could you tighten the gas enough to cycle blanks?

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.