Or you could try swapping your barrel with somebody, and git you one with a removable choke. That way, you can try one of the compensated chokes on the market. If you don't like it, toss it.
If you go ahead with the homee-brew method, at least buy yourself the drilling jig available through Brownells. It'll keep your bit from walkin on you, and gives you a predetermined pattern of holes that's known to work.
Edited to add - The best way to make sure a barrel uncontrollably rusts for the rest of your life is to not use metal etch or not soak it in oil after exposing bare metal to the outside world. Make sure to drop the end of the barrel in a bucket of oil for awhile after drilling, until you reblue it.