KerbalX

Project High Altitude Research Project (yes two Projects) was a 1960’s US-Canada ballistics research program famous for its extremely large gun. It had the ultimate goal of eventually launching satellites into space. Though it never launched anything to orbit, it did collect quite a bit of data from the upper atmosphere using the martlet projectile, reaching an altitude 181 km. It was built by welding two 16-inch battleship canons together!
[1] to lift the barrel (it takes a while). [2] to fire - only one shot.

I recommend you research this thing; it’s quite interesting. Here’s some info:
Wikipedia: https://en.wikipedia.org/wiki/Project_HARP
A site with some nice images: https://www.bajanthings.com/high-altitude-research-project-harp-1962-1967/
An archived news reporting: https://youtu.be/gUcuda7tLa8

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If you decide to download this make sure to disconnect this strut before lifting the barrel.