So with a gun, can someone literally "blow their head off" or "blow their brains out"?

Of course I’ve often seen in soap operas on TV and things like that where someone says about someone who has used a gun “Oh yeah, he blew his head off” or “Oh yeah, he blew his brains out” but I would like to know more about this. Actually what the Straight Dope is on all this and things like that. Does anyone know from a medical viewpoint what happens here? Or does anyone know anything else about this then?

Use Google Images to look up “shotgun suicide” but not on a full stomach. The answer to both is yes, or at least the majority of your head.

Rifles and handguns can at least cause some of your brain matter to be ejected through the exit wound as well.

Agreed. The type of trauma heavily depends on the caliber of the munition and muzzle velocity. I have seen some people in wartime that suffered significant deformation of the skull and the evacuation of a large amount of cranial matter. Literal decapitation might be rare, but with a sufficiently large bore/caliber it is not beyond the realm of possibility.

High power rifles and shotguns can literally blow your head open. Pistols usually create an exit hole but with hollow points turn your brain to mush.

I’ve seen a photo of someone who [del]caught[/del] received a .50 cal bullet in his forehead. There was still a face but not much at ALL behind it. I think “caught” was the wrong word as it kept on going after destroying the skull.