SpudFiles

Lentamentalisk wrote:The issues here are that A) there will be lots of high pressure air behind that piston, and it will have to go somewhere. Vent holes would solve that.
B) that piston is going to be moving FAST. In fact, that piston is going to be moving exactly as fast as the nail, which means that it will have a fork-ton of kinetic energy. When it collides with what ever sort of bumper you stick on the end, to keep the piston from leaving, it will either smash it to pieces, or if you make the piston light enough to not smash the bumper to pieces, it will smash itself to pieces.


That being said, it has been done before. Some silent guns, designed for secret agents have used this technique to contain the gases until they cool. Also I believe they made a few grenade launchers that function similarly.

Lentamentalisk wrote:That being said, it has been done before.

Some were evaluated but none was adopted by the BEF, although the French made limited use of a 105 mm pneumatic mortar which the Germans then copied. Such mortars were largely silent and produced no muzzle flash so that they were difficult to detect but they were more complex than conventional mortars and had slow rates of fire. Noise and flash were the tell-tale signatures of a trench mortar which, once detected, often prompted a retaliatory artillery bombardment. Almost from the outset, inventors began experimenting with attachments to suppress muzzle flash, smoke and noise but only one, the Temple silencer, was adopted.

This was invented for the 2-inch medium mortar which was particularly loud and produced a considerable muzzle flash and a limited number of silencers were available from spring It comprised two elements: a muzzle attachment in the form of a chuck, with spring-loaded cones, which restricted the bore at the muzzle to 1.5 inches; and an obturator at the base of the stem. The bomb now had to be fitted with a stem of 1.5 inches diameter, rather than 2 inches, but which widened where it joined the body of the bomb to allow existing bombs to be used with the silencer. The obturator served to centre the stem in the bore and to prevent the propellant gas escaping from the muzzle. It was an imperfect solution, however, as it caused the barrel to overheat which severely reduced the rate of fire. An overheated barrel could cause misfires and prematures.

Prematures were a constant problem with trench mortars. Up to fourteen casualties a week could be attributed to prematures with the 2-inch mortar. No more than six rounds could be fired at the rate of one round a minute before the barrel had to be cooled. Thus, silenced mortars tended to be used only for night firings when muzzle flash was especially noticeable. The silencer could be fitted and removed quite easily so that dedicated silenced mortars were unnecessary. To load and operate a mortar fitted with the silencer was a rigmarole, especially after having discharged a round. The silencer worked by trapping most of the propellant gases in the barrel which then had to be released by opening the chuck. At the same time, the obturator, which had been stripped from the stem on firing, was ejected from the muzzle. Trapping the gas caused condensation in the bore which had to be sponged out after each round. It was a far from ideal solution although it did perform the job it was intended to do.