Silencers

Question
Can silencers be used with blank rounds or would it not silence the escaping gasses? For example in a movie scene where a silenced weapon is used, would the silencer sound the same if real bullets or blank rounds were used?

Answer
People who use gun silencers actually call them suppressors. The sound of normal gunfire has two parts: the sound of the gases escaping at supersonic speed, and the sound of the bullet travelling at supersonic speed. The suppressor includes a baffle that provides an expansion and cooling volume for the gas so that it exits the barrel at a speed lower than sonic speed. The cartridge selected must also be made so the bullet speed is reduced to below sonic speed. The most popular suppressed caliber is .22LR. These bullets will be subsonic if you buy "standard velocity", but not the more popular high velocity, or hyper velocity loadings (they are supersonic and will make a loud crack even with a suppressor).

So, with a suppressor, you also need to have a subsonic bullet if you want it to be quiet.

When firing a blank, the gases expand at a different rate from when using a bullet, and a normally designed supressor may not work as well, because they are designed for the pressures and gas velocity developed with bullets. It will probably be close enough and work OK with a .22LR rifle, but not as well with a pistol, or with larger calibers.

I don't know of anyone designing a suppressor specifically for use with blanks (as you probably know, the quiet guns in the movies are just created by changing the audio track. The sounds you hear in the movie are not the ones produced by the gun. Many movie guns are actually compressed air powered, and are not real guns.)

Hope this helps!

Dave