How to conserve a used gun

[WAB]

I would love a cannon. My house is situated perfectly for one!

 

[VertigoBE]

I have a fun one on my hands! A friend dropped off a CANNON for me to conserve for him. It shot a line and was used on naval boats to shoot a haul line with a floatation device. “We’re here to rescue you, now let me aim this cannon full of black powder at you”.

It should be a fun project. It weighs about 300lbs.

Pictures please!