I've written extensively in the past about the General Electric 20 MM M61 autocannon which I worked with in the USAF...I won't bore anyone here with more trivia about that one, but I thought some of us might have an interest in one of its predecessors, the Oerlikon 20 MM autocannon, of which my uncle's ship during WWII, APc-48, carried 4...All hands were trained to operate the Oerlikon although my uncle never spoke of firing one...Pictured below is a restored Oerlikon borrowed from the USS Texas (BB-35) while it is undergoing its own restoration...Photo credit goes to an unknown blogger...

Below that the first video shows another restoration which was being auctioned......Ben