Thank you Eat Uranium.
It's been said the M3's armour (roughly 8 mm) was inadequate against machine gun fire (Hanomag = 6-14.5 mm), but you are right - the MG42 probably couldn't cut it. I've read some accounts of German machineguns taking out halftracks, but I suppose those particular Germans shot rather well.
Anyways, thanks a bunch.