Free oil barrel, had new 5-30 in it. I picked one that had new oil as opposed to used so I new that there had not been any gas in it for grinding safety.
I laid it on its side and used an angle grinder on the outside top corner at about 30 - 45 deg in relation to the side of the barrel.
Grind until you just see the 2nd layer of metal and continue all of the way around the top.
Make a mark on the top and side for re installation then grab the top through the big bung and pop it off.
You WILL have a razor sharp edge on the top that will have to be dealt with.
I filed mine flat with minor blood loss.
I then drained out the 3/4 qt of oil left in the barrel and poured it in my car, then left the barrel upside down in the driveway for a couple of days while I made the charcoal basket etc. Then I washed it out as well as i could, drilled 3 13/16 intake holes, (13/16 holes fit wine corks perfectly), loaded up the charcoal basket with KB and fired it up with the top off and let it go for an hr or so, then dropped the top on with both bungs out and let it go until the charcoal was gone.
The next day I dumped out the ashes etc. and scrubbed out the varnish made by the oil left in the drum added the bolts for the racks, coated with veggie oil and burned one more load. There was no more oil smell or anything so on the next day i cooked a cheap fatty which came out fine.
I've been cooking on it ever since.
Still has the original paint but I did pull the 5-30 sticker off the top.
YMMV
Steve