I have to admit, it's not my idea. I got it from a member in my team as a way to convert a G&P 130 round midcap into a standard 68 round magazine. I know many who have done it, and they all describe it as an easy mod, but maybe it's easier to do this with a midcap than it is with a standard magazine? I will try to convert a 68 round magazine to 30 round capacity this way and get back to you with the results.
Cheers