NOISELESSNESS.
A great many stories have been told about the noiselessness of smokeless powder. But there is no such thing as a noiseless gunpowder. The report of a gun charged with smokeless powder is very sharp, and is as loud as when black powder is used, yet the volume of sound is much less, so that the report cannot be heard at so great a distance.
The report of a gun using smokeless powder is a sound of much higher pitch than when black powder is used, and consequently cannot be heard at so great a distance as the lower notes given by black powder.
As smokeless powder exerts a much greater pressure than common black powder when burned in a gun, one would naturally think that the recoil of the barrel would be greater, owing to the greater pressure exerted by the smokeless powder on the base of the cartridge case and the breech mechanism. However, such is not the fact; for the barrel actually recoils very much less when smokeless powder is used. This is due to the suddenness with which the pressure is exerted by smokeless powder, it acting more like a very sharp blow on the metal, whereby more of the energy is converted into heat instead of being spent in overcoming the inertia of the barrel to give recoil. Similarly when smokeless powder is fired in a gun, the displacement of the air is so sudden that the sound waves do not possess the same amplitude of recoil or vibration as is given by black powder.