https://www.rockislandauction.com/detail/70/2502

The 20mm Oerlikon automatic cannon was a mainstay of United States naval air defense during World War 2, and today we will look at a few of the characteristics and questions that apply to this sort of automatic cannon but not to typical small arms. Like, for instance, how do you cock a gun that has a 400 pound recoil spring? Or, what happens if you fire a high explosive shell into your muzzle cover?

http://www.patreon.com/ForgottenWeapons

Cool Forgotten Weapons merch! http://shop.bbtv.com/collections/forgotten-weapons