The Oerlikon 20 mm cannon was first used during World War I. Various models of Oerlikon cannon were used during the Second World War, and they are still in use today by US, British & derivatives by Germany & Japan. Some were mounted in aircraft but most were used as anti-aircaft guns on land and sea. It could fire at 450 rounds per minute and had a range of 2000 metres. Ammunition feed is by a 60-round drum magazine on the top of the gun. Both single and twin configurations were used.The parts are all oriented for assembly. Some like the shield and the sights need to be rotated so that they are printed flat and thus don't need supporting structures.There's one OBJ file with all the parts in it and then ten separate STL files. The only missing part is the rod that connects the front and back sights. You could use a pin or a piece of thin wire for that. All parts are at 1 in 33 scale.

PARTSbaseshieldfront-sightpivot-mount-leftpivot-mount-righthandle-arm-Lefthandle-arm-rightbarrel ( including sight arm)magazineback-sight