The Gasser-Kanardly vacuum gun!
by B.B. Pelletier
You know how I like to tell tales of vintage airguns. Well, today, I have one that's more than vintage--this one is nearly mythical! It's the 1927 Gasser-Kanardly vacuum gun.
Ferdinand Gasser was a German tool maker who had an interest in airguns. He knew about powerful precharged guns like air canes, and there's evidence that he may have even made one or two canes. But his most famous airgun has got to be the 1927 Gasser-Kanardly vacuum gun.
We all know that a PCP works by expelling a pellet with a huge blast of air behind it. Well, Gasser wondered how effective a vacuum AHEAD of the pellet would be! His early experiments proved that a vacuum was not enough to start a lead pellet on its journey. He evacuated all the air in front of pellet after pellet, and they either remained in the breech as an effective plug or were slowly sucked down the barrel as friction was overcome. But the velocity never rose above about 50 f.p.s. That was estimated by means of a ballistic pendulum, which was all that was available to him in that day.
He also had several technical problems with the design. One was getting the muzzle to open in time for the pellet to shoot out. The vacuum apparatus had to keep the muzzle sealed to keep the vacuum as high as possible, but it also blocked the pellet's path. That meant that the ballistic pendulum had to be placed inside the vacuum chamber, which made it the size of a small room!
The other problem was the size of the vacuum apparatus. It was many times larger than the gun. While good for a laboratory experiment, it wasn't convenient for taking the gun to the field. Fortunately, he overcame both problems and also got a super boost at the other end to increase velocity above 750 f.p.s., for a .22 caliber pellet. This all happened when he had the good fortune to meet Trevor Kanardly, who was attending university in the same Bavarian town where Gasser lived.
Kanardly was the son of a wealthy British shipping magnate, who had sent his third son to Germany to study physics. But Kanardly was something of a playboy who was more interested in parties, young women and riding around the countryside on a BMW motorcycle. However, he soon befriended Gasser, who tutored him in his physics studies so he could remain at university.
When he learned of Gasser's gun, he quickly solved both problems with an ingenious solution. He suggested a barrel jacket to contain the vacuum. He reasoned that the volume of the vacuum only had to be large enough to compensate for the volume of the bore and could, therefore, be quite small. Gasser quickly saw the genius of this and made a small barrel jacket to hold the vacuum. Small holes in the side of the barrel at the muzzle allowed the air to be evacuated from the bore.
The other good idea was a frangible plug at the muzzle that the pellet would shatter on its way out. Bavarian clay soil--very much like gumbo--proved the ticket when mixed with beer, of all things! It made a natural plug that was strong enough to withstand the hard vacuum, yet shattered like glass when struck by a lead pellet moving faster than 300 f.p.s. The same material was later used in the German Air Force ramjet project as a plug to keep the air intake closed until the air velocity had reached ramjet speeds.
The plug worked, but the pellet still had to be shot through it and the vacuum wasn't strong enough to do that. So, Kanardly suggested putting a spring piston on the other end of the gun. That was the solution Gasser had been searching for! It turns out that a lead pellet pushed by a vintage spring-piston powerplant might only get up to 500 f.p.s when it has to fight normal air pressure, but when shot into a vacuum, it races well past 800 f.p.s.! Some energy is lost breaking through the frangible muzzle plug, but Gasser recorded many velocities at or above 750 f.p.s.
The two prototype guns he built were indeed portable enough to be carried and shot, though the support equipment consisting of a vacuum pump and extra muzzle plugs had to go with the guns in a motorized transport. Both guns and all supporting equipment was destroyed in World War II, and all we have today is a couple of reports written in the German gun magazine Visier.
A British airgunner stumbled on the Gasser-Kanardly design in 1996 and used modern materials to build a copy of the gun. It actually worked much better than the original because the spring-piston powerplant he used was so vastly improved over what was available in 1927. Reportedly, Nigel Andersen of Surrey was able to get .22 pellet velocities in excess of 1,000 f.p.s. He had to substitute a chalk plug for the Bavarian gumbo plug, and it didn't seal, so he used a rubber seal on the muzzle side.
Andersen's gun was reported in a special edition of Air Gunner published June 31, 1999. He was also fortunate that modern vacuum pumps are so much more efficient than those used by Gasser and Kanardly. In Andersen's own words, "This thing really sucks!"
I want to wish all of my faithful readers a happy and pleasant April first!