Say you line up a bunch of people’s heads in a line, all touching one another, and you put the gun on the first guy’s head, how many people will be killed when you fire?
Depends on the gun.
22? Not so many.
50 cal - a whole lot.
Depends on the gun and the specific cartridge you’re using.
A .50 BMG will go through a lot more than a .22LR.
ETA ninja’d by a think alike mind.
If you’re referring to, say, a typical handgun - let’s go with a Glock as the example - I don’t think it would kill any more than 1 person. The bullet would be slowed down too much by the first person’s skull (bear in mind, the bullet has to pass through TWO layers of bone before it gets to the 2nd person) to cause death to the 2nd person.
That’s not even taking into account the fact that the bullet may be deflected within the 1st person’s skull so that it might not even hit the 2nd person.
Shove the bullet down the first guy’s throat until he chokes to death. Then fish it out, and repeat with the second guy, and so on.
The skull is pretty thick, so you’re not going to go very far with a handgun that way. You’d have a much better chance of multiple kills if the bullets go through the chest and manage not to hit ribs along the way.
Here’s a story of a sniper who killed six Taliban with one bullet. To be fair though, he hit a suicide bomber and his explosives detonated, taking out five of his Taliban buddies. That’s probably not what the OP intended.
There’s a scene in Schindler’s List where a death squad lines prisoners up in single file and points a rifle point-blank range. . . maximizing carnage per bullet.
A 9mm FMJ will easily go through one side of a skull and out the other, with plenty of Velocity left to do it again.
It would depend on the bullet type and power factor. A 9mm FMJ certainly can kill more than one person.
On the other hand, a 308 solid steel bullet will pass many.
I suppose if you lined people up behind each other and had them open their mouths and had them lined up in such a way that you could shoot the first one in the mouth so the bullet went through the back of his head and into the next guys mouth and through his head and so on. Then I suppose you could kill more than 1 with a handgun. It would minimize how much skull material the bullet would have to travel through to kill them.
The faster the bullet the more this would be successful is what I think.
First, how are you going to get people to line up for the experiment?
Must we shoot heads? Seems sort of boneheaded to try to penetrate the most bone you can.
Battle ships have big guns, you did not say which guns could be used so I will use one of them.
As was said in a post above, this will kill a lot.
Glad I passed my background check before I posted in this thread. 
If you line up the heads sideways you will be shooting through the temporal bones which are thinner than most of the skull . I don’t know what this means in number of heads penetrated
Shooting through an open mouth so the bullet goes through the back of the head is shooting through a minimal amount of bone yet causing maximum damage. Plus, where else on the body could you shoot through one person to hit another with less resistance but still cause instant or near instant death?
Eye.
Higher probability of kill as its going into the brain easier than thru the teeth/roof of mouth.
It’s a shame Arlen Specter isn’t alive anymore as he was an expertry on single bullets.
I was going with the U-235 bullet in the Thin Man device exploded over Hiroshima … but I think you got me here …
where are Mythbusters when we need them?
The Thin Man was a series of somewhat farcical detective films starring William Powell and Myrna Loy. The bombs dropped on the Japanese cites of Hiroshima and Nagasaki were the “Little Boy” and “Fat Man” respectively.
Stranger
Thanx for the correction.
The Navy has a fairly new laser gun that is so powerful that they claim, if you put a line of thin people standing closely together they can shoot through 2200 people per mile for a distance of aprox. 900 miles. Adapting for the curvature of the Earth would be necessary.
The Laser Weapon System would not really hurt them with hard nasty projectiles, rather, when shot, it would just put a one foot circular hole in each of their bodies and would just keep moving through.
The NRA is petitioning the US govt to allow the manufacture of, and public gun show sales in the South, and in Chicago.
This human carnage is fast and painless (almost humane), too. This very effective high-energy device can strike “this line of peeps” at the speed of light (186,000 miles per second)!
The cost? Less than a dollar per shot.
My math is suspect…what would therefor be the cost per kill with this weapon?