[Paul On The Run]

a heat gun will take forever to remove the glass. There is some crazy haenous glue that holds the mirror in place. I've found that baking the whole thing in the oven, mind you prior to any powder, that it will soften the glue enough so you can pull apart. Actually if you lay the mirror glass down and after about 15-20 minutes of a good sustained 300 degree temps, when you go to lift the mirror the glass should just ooze off so to speak.

...and I'm assuming these are stock HD mirrors.