I just used a large screwdriver, hammer, and a pair of vise-grips. Add in some swearing, and a friend on the sidewalk in front of his house, and viola! 440 rounds ready to go!
Though I just picked up an angle grinder the other day, and will probably use that in the future. As for the lid, it may have been mangled, but I took it into the shop, and used a hydraulic press to mash it back to flat.