Originally Posted by Pirate-Drakk
The compression wave pushing the round out of the barrel is also supersonic (as it leaves the barrel). The projectile can't move faster than the thing pushing it...
Perfectly true but it has nothing to do with suppressing the sound made by the round passing through the air. Indeed I don't think anyone has solved this problem on any weapon yet.
Perhaps the earliest semi automatic weapons used on the battlefield were air rifles. From about 1700 air guns were the province of rich hunters but at the end of the eighteenth century (in 1790) Austria had equipped a unit of Jaeger with repeating air rifles with the butt containing the air reservoir.. The guns were the invention of Bartolemeno Girandoni an Italian ex clockmaker whose first gun had appeared in 1779. Some 1,500 were produced.
Some fantastic claims have been made for the rate of fire and range of these weapons, it has been suggested that 500 men could fire 300,000 rounds in 30 seconds and be deadly at a range of 150 yards. These claims are just that, fantastic. Firstly the effective range of the weapon was 100 yards but only for the first ten shots fired, after that the pressure in the reservoir had dropped so much that the next ten shots would only be effective at 80 yards. After that the range dropped so drastically that the reservoir had to be recharged if the gun was to remain effective. Charging the reservoir required over 200 vigorous strokes with a heavy hand pump. Even with a fit soldier this could take over six and a half minutes, loading more rifle balls into the magazine would take perhaps another minute. This meant that whilst the soldier with an air rifle could loose off 20 rounds in a minute it would be another seven and a half minutes before he could repeat this. The hourly rate of fire for 500 men would therefore be about 75,000 rounds. As an alternative to having each soldier pump up his own reservoir wheeled pumps driven by a hand turned wheel were introduced in the ratio of one every ten men and runners were supposed to supply the troops with fresh recharged reservoirs. This would substantially reduce the flexibility and manoeuvrability of the unit.
The effective range of a musket was about 80 yards; most European armies could manage a sustained rate of fire of about two rounds a minute. A well trained regiment in Wellington’s Peninsular army could manage between three and four rounds a minute (and up to six for short periods). This would give 500 men in an ordinary European army an hourly rate of 60,000 rounds and for a crack British regiment between 90,000 and 120,000 rounds.
The air rifle was capable of very high rates of fire but only for short periods after which the soldier using it needed to retire behind cover to pump up the reservoir. This meant it was best used in skirmishing, which is exactly what the Jaeger were intended for. In this role the lack of smoke to reveal a rifleman’s position would be a bonus. Unfortunately Austrian tactical doctrines of the time was very rigid and focussed primarily on the movement of formal bodies of men and not at all suited to the effective deployment of riflemen. The expensive Girandoni guns were also mechanically unreliable if used for any length of time and from 1800 they began to be replaced by conventional flintlocks. The gun was used against the Turks and the Russians but by the time that Napoleon’s troops marched towards Vienna the air rifle had all but vanished from the Austrian service.
During the nineteenth century the air gun was primarily viewed as an assassin’s weapon. In fiction one of Conan Doyle’s villainous characters, Col. Sebastian Moran, commits murders with such a weapon and attempts to assassinate Sherlock Holmes in the same manner. Some gunsmiths produced gentlemen’s canes that concealed powerful single shot airguns. Weapons of this type were adopted by some secret services and may still be part of their armoury to this day. In London in 1978 the Bulgarian defector Georgi Markoff was fatally poisoned by being shot with a ricin pellet fired from an air gun disguised as an umbrella. The Bulgarian secret service has been implicated in this assassination. During the Second World War Britain produced some air and gas powered weapons for use by intelligence and sabotage agents these included ‘fountain pens’ that fired tear gas. It is quite probable that other very special forces around the world have access to similar deadly ‘toys’.
The Czechoslovakian armaments industry produced a military air rifle in the 1930s.What it was used for and by whom remains unknown. It is possible that it was intended for training.