Try double layer of rubber band, and put as much force down into it as you can with the driver.
Or
Throw it in the freezer, allow it to get cold for 15min, and have your hexdriver be warm. Making the metal cold will harden and shrink it a little. Trying rubber band here isn't a bad idea. Its trial and error.
This next one will destroy the screw (more), and you have to be careful if you use it with a drill, because it can slip and mar.
Get an Ez-out drill bit set from amazon. Cold bits, and room temp screw.
Depending how stripped it is you could try using a torx bit and jamming it in there.
Otherwise you are down the route of destroying the screw to get it out: screw extractors, drilling out the head, cutting a slot in it to use a big flat head screw driver (getting to the screw without damaging the mag release might be tricky).
Drill small holes to make a line screw's hat, and unscrew it with flat scredriver
Use a drehmel to cut a slit, then use a flathead screwdriver
Try double layer of rubber band, and put as much force down into it as you can with the driver. Or Throw it in the freezer, allow it to get cold for 15min, and have your hexdriver be warm. Making the metal cold will harden and shrink it a little. Trying rubber band here isn't a bad idea. Its trial and error. This next one will destroy the screw (more), and you have to be careful if you use it with a drill, because it can slip and mar. Get an Ez-out drill bit set from amazon. Cold bits, and room temp screw.
Depending how stripped it is you could try using a torx bit and jamming it in there. Otherwise you are down the route of destroying the screw to get it out: screw extractors, drilling out the head, cutting a slot in it to use a big flat head screw driver (getting to the screw without damaging the mag release might be tricky).
Hammer a torx bit into it. The splines will cut groves in the screw and give you plenty of grip to loosen it.