No!!!!!

No mag whacking!

Remove your upper, and insert the mag so you can see where it's rubbing on the lower.  Usually, it will be the top rear cubic inch of the mag.  The mag is weakest here because of the cut-out at the rear for the bolt stop, and tends to swell with use (mostly during loading).

The fix is to GENTLY and SLOWLY squeeze the mag until it drops free.  I use a (padded) vice, but you can also use a C-clamp, channel locks, or whatever.  The key is to go slow, and check often, because you're only wanting to change the dimension a couple of thousandths of an inch.  Use something to pad your squeezing tool (tongue depressors work great!).

-Troy