No filing or grinding necessary - just bend it in a vice.
(Although I did chew mine up a little because my vice jaws weren't too good...)

I bought my partner a small cooking gas blowtorch for Christmas (she's French and a wiz in the kitchen), but the only thing it's done so far is to help heat my BAD lever for bending!

Result:





NB - it needs to have a bit of space from the receiver so that the offside of the mag release doesn't push on it when releasing a mag, otherwise, it'll snap the bolt shut again!