Well, what I did, was a lubed up the gas key, and then I shot it, after 40 rounds it worked smoothly. However, I don't think mine was as tight as others.
Other things you could try, is measure, your gas tube and see if you could find a drill bit the same size.
Drilling out the gas key, I don't know if I like that idea, mess is up and you have a bad seal.
Another trick is to rig a piece of sandpaper as the end of a dowel. Given the size of the gas key, maybe a 17cal jag will hold a piece, spin it in there with a drill to lap it.
What I would probably do, is remove my gas tube, put one end of it in a drill, and then spin it while holding a piece of sandpaper on the end that mates with the gas key. Lap it down till it fits tight with the gas key.
Tight but not smooth. Fit it so that you still have to kind of force it, but it's loose enough you can get it on and off, then fire the rifle till it breaks in.
I'm worried that even after you fit it, something else will go wrong. Some people who have reported the BCG fitting fine, and have been using it, have suffered bolt failures.