A peripherally related comment: I bought a can opener of the type that cuts the can lid crimp ring from the side (instead of the lid itself) and I use it frequently to make shop storage containers since the separated lid still fits and seals onto the can. I've even been known to go to the grocery store looking for some food in a container that's about the right size that I need to later use once the food's gone.
Attachment 35162
If I have to torch cut into a barrel after emptying it, I always flood the barrel interior with Argon from my TIG torch first so if there's any flammable vapor remaining there's no oxygen in the barrel to support combustion.