Actually, if you're right-handed your left hand will be more like 8-10" from the breech, not the muzzle (which is the very end of the barrel). This is where one's concern should be regarding the wall thickness, and that measurement (minimum wall thickness)is what is given by conscientious vendors for a shotgun they're selling.
Many people have their own standards as to what they consider safe, but .025 seems to be the general consensus as to what is acceptable for the minimum wall thickness in this area.
Now stand back so as not to get burned from all the flames that will come my way for spreading this very general theory.
