The Girandoni air rifle.
The rifle was 4 ft (1.2 m) long and weighed 10 lbs (4.5 kg), about the same basic size and weight as other muskets of the time. It fired a .46 caliber ball at a velocity similar to that of a modern .45 ACP and it had a tubular, gravity-fed magazine with a capacity of 20 balls. This gravity operated design was such that the rifle had to be pointed upwards in order to drop each ball into the breech block. Unlike its contemporary, muzzle-loading muskets, which required the rifleman to stand up to reload with powder and ball, the shooter could reload a ball from the magazine by holding the rifle vertically while lying on his back and operating the ball delivery mechanism. The rifleman then could roll back into position to fire, allowing the rifleman to keep a "low profile". Contemporary regulations of 1788 required that each rifleman, in addition to the rifle itself, be equipped with three compressed air reservoirs (two spare and one attached to the rifle), cleaning stick, hand pump, lead ladle, and 100 lead balls, 1 in the chamber, 21 in the magazine built into the rifle and the remaining 80 in four tin tubes. Equipment not carried attached to the rifle was held in a special leather knapsack. It was also necessary to keep the leather gaskets of the reservoir moist in order to maintain a good seal and prevent leakage.
The air reservoir was in the club-shaped butt. With a full air reservoir, the Girandoni air rifle had the capacity to shoot 30 shots at useful pressure. These balls were effective to approximately 150 yards on a full load. The power declined as the air reservoir was emptied .
en.m.wikipedia.org/wiki/Girandoni_Air_Rifle#section_2
A VERY SPECIAL GIRANDONI SYSTEM AIR RIFLE
Made in the 1940s during WW2, this gun doesn't look like a Girandoni, but examination shows that it clearly was built by someone familiar with the Girandoni repeating airgun system. Purchased in Europe, the story is that this gun was built somewhere in occupied Europe by a partisan bicycle maker during the Nazi occupation in WW2 . (Originally we suspected that the maker was in Austria but an Austrian friend pointed out that there really wasn't any resistance movement in Austria - most Austrians still considered Germany and Austria as a single unit, as it had been in the past, and actually welcomed the Nazi troops when they occupied the country, virtually without force.) The repeating magazine is spring fed and on the left side of the barrel, for the convenient use of a right handed shooter. The gun was charged with the accompanying bicycle type pump. Smoothbore, as would be expected, but firing a 11 3/4 mm lead ball (.464" caliber) (the very same caliber as the original Girandoni Austrian military repeating air rifles!), this would have been a fearsome weapon against sentries, drivers, military leaders, etc. at ranges up to perhaps 100 yards. To a freedom fighter, the lower discharge sound and the lack of flash or smoke would have been huge values. And it did not need powder, primers, or bullets - only easily cast lead or soft-metal balls! The builder surely drew his inspiration from a museum, or even just a book, which displayed a Girandoni system airgun. The excellent quality reflects the experience of a perfectionist bicycle maker with considerable time on his hands - consistent with such a craftsman in an occupied area.
Note that this gun has a spring fed magazine, rather than the gravity fed magazine of the original Girandoni military air rifle. While a gravity feed mechanism might be simpler, and even more dependable, the spring fed magazine has great advantages for the purposes of this gun. It is more suited for operation from a vehicle or firing slot where it would be impractical to tip up the rifle for loading and it allows firing with minimal motion at the firing point - very important to a sniper.
Why would a modern sniper want a functional version of an ancient airgun when automatic weapons were as close as the first German soldier that could be waylaid? The answer dramatically comes from the above notes and the fact that an American maker is now doing a small, but excellent, business supplying coalition troops in the near East with high power 9mm repeating PCP air rifles, complete with silencers and nightsights. Unlike a firearm, such a weapon, without sound, flash, or smoke, does not attract return fire - esp. in reduced light situations - the deadly projectile just seems to come from no-where!
Basic specs: A husky 12.2 lbs., 45" overall, glare-free, w/ almost camo anodized type finish.
www.beemans.net/Austrian%20airguns.htm 
