Swiss Solothurn SU 100 20 mm
These automatic 20 mm weapons were used a long time in Switzerland. They had fortress version, anti aircraft version , anti vehicle is the one one the wheels, one version was semi and the other was selective fire. I shot 2 rounds with one and I was astonished by the low recoil absorbed by the hydro pneumatic system and the accuracy at long distance, on the pix you can see the scope,
Photo from: ? Information from: The Frog Man
