Well gentlemen in regards to ricochets from the 38, I will state that during my numerous schools as an instructor that I was required to attend, and this very topic was covered MANY TIMES.
A bullet WILL IN FACT change directions if not of the proper configuration. If glancing off the skull a round nose will glance off REGARDLESS of whether the skull moves or not. It has nothing to bite into, as will also a 230 grain ball round from a 45acp.
The movement of an almost weightless balloon is not a good comparison to a human head that weighs eight pounds or more, and is attached to the body by the neck.
I have personally seen the latter happen in an actual shooting involving a stolen 1978 Buick in 1978. An officer put two rounds into the windshield head on, and neither round penetrated but instead glanced off, or ricocheted if you prefer. The bullets had not bite to them or, shoulders if you will, to dig into the glass, and simply changed directions.
It is indeed all about "bullet configuration" and can be demonstrated easily with a bowling pin, and a short interview with anyone whom has ever competed in the bowling pin shoots. A round nose will glance off the pin, and though probably knocking it down or moving it slightly, transferring little energy to the pin, where as a flat nose such as a waddcutter or semi-wadcutter, or a FLAT NOSE will BITE into the pin if it is hit on the side, and SPIN the pin, rather than glance off transferring much more of it's energy to the pin.
It is the same principle with the human head.
Now, I have basically I think, concurred with much of what Mikey has said, with a twist to the head shot. I have seen the head shot NUMEROUS TIMES, for real, and bullet configuration is very important as Mikey said, unless it is a dead on shot.
Another principle many do not know is that a 9mm ball round will many times OUT PENTETRATE a 357 magnum, and in the old days of bullet proof vests, they were feared more. Why? Bullet configuration! The 9mm had a sharper nose, and delivered more of it's energy in a smaller area than the wider faced 357 mag. That's why the 357 sig, which is not a 357 at all (was dubbed so for advertising), can never out perform consistently the 357 mag. It's hollow point design is totally reliant on available body liquids and their hydraulics. One does not have to agree, but balistiticians whom are not selling guns, but testifying in court rooms will say this. I ain't smart, I just listened when trained.
So Mikey, for the most part I am agreeing with you, with a slight twist.