Volunteers at the US Air Force Museum in Dayton, Ohio, are close to finishing the restoration of an A-10 Warthog's Gatling gun.  A project that was started 10 years ago is close to completion as missing parts had finally been acquired.  According to the Air Force Museum's website, it's the most powerful gun fitted to an aircraft. The 30mm gun can fire 4,200 rounds a minute, and will be on display soon.

Volunteers working on gun