Would this require the shells though? Does the damaging part of the bullet have unique marks? If so, how?

Dave (as curious as Lisa)

As I understand it, as the bullet leaves the barrel of the gun, it takes on markings of the boring of the barrel. This leaves little marks on the bullet that are identifiable to the gun.

Is it possible to tell (without the gun as evidence) that two bullets fired into different people were fired from the same person's gun? Or would you just be able to tell they were shot by the same type of gun?

To answer your second question first, it's easy for the most part to identify the TYPE of gun.

It's done by the number, width, and depth of the lands and grooves in the rifling of the barrel. Most handguns for example have six lands and grooves.* Some custom barrels have 8. All Smith & Wesson barrels -- whether revolver or Auto-loader -- have five lands and grooves, which makes them very easy to identify. (Modern S & W's that is, I don't know about antiques.) But you have to be careful here. It's not uncommon for a gunsmith to put a Colt Python revolver barrel on a Smith & Wesson. Python barrels are very accurate.

To actually determine if two bullets were fired from the SAME gun is not so easy. Much of this depends on the TYPE of bullet fired. Bullets cast of soft lead can be impossible to identify as some lead often sticks to the inside of the barrel changing the identifying marks with each bullet fired. In this case, spectro-analysis of the bullets is necessary. In the case of mass produced cast bullets, it can be impossible.

The same is true of copper jacketed bullets -- especially in rifles -- and for the same reason; copper coating of the barrel.

If someone were shot by a person using a gun which hadn't been cleaned for a while, and then shot someone else after the gun WAS cleaned -- and using different ammunition -- it would be impossible to tell . . . except that it was the same KIND of gun.

OR are there any guns/ammo so rare that finding two people shot by that gun would almost certainly mean that they were shot by the same person?

The answer to that question is definitely YES! Well, shot with the same GUN anyway.

Sorry if these questions sound stupid. I'm kicking around a story idea, but I know next to nothing about weapons.

Lisa

NOT stupid! Shows you're thinking. But they are pretty general questions, and therefore get pretty general answers. If you're writing from the perspective of a forensic criminologist you would be looking for one thing. If you are writing from the perspective of a knowledgable criminal trying to escape detection you would be looking for something else.

Ken V.

*More than you wanted to know.
Lands and grooves -- when making a rifle or pistol barrel, the barrel is first bored to a certain hole diameter, let's say .300 inches. This is the bore diameter.
It is then "rifled," i.e., metal is removed to create spiral grooves down the barrel. In this case the grooves have a diameter of .308 inches, hence the term groove diameter.
The sections that still have the bore diameter are called Lands. The bullet diameter should be very close to the groove diameter so that the lands will "squish" into the bullet and give it a rotational spin. The purpose of this is to give the bullet stability in flight -- like a gyroscope.

I am giving myself semi-partial credit for my answer.

Scott

In your story, are you trying to get a gun identified? Or are you trying to KEEP a gun from being identified?

The rifling from the barrel of any gun will show up on a bullet. Even if two bullets are fired at two different people.
The only exceptions to this that I know are:
1. the weapon fired was a shotgun (no rifling exists in most shotguns...they spray little lead balls) or

2. the person uses a sabot round (most pistols don't fire sabot rounds...it's a rifle thang). A sabot is a false covering, such as paper or hard plastic, that falls away from a bullet after it exits a barrel. It imparts a spin to the bullet that maintains accuracy, but protects the bullet from getting marks on it.

If the gun is an semi-automatic (or machine gun) then spent cartridge cases will litter the ground. From these, you have two identification points typically.

1. Firing pin marks on the shell
2. Extractor marks on the shell (scratches on the shell where the little thingy pulled the shell out of the barrel after you fired the gun.)

I am giving myself semi-partial credit for my answer.

Scott

Deserved credit.

But here's something interesting:

The FBI did some additional testing a few years ago on the rifle that was used to kill Dr. Martin Luther King back in 1968. They fired a number of rounds through the rifle, recovered the bullets, gave them to their crime lab, and asked them to identify how many rifles fired the bullets.

There were nine or ten bullets IIRC, and the crime lab said that there were four different rifles used . . . all of them different from the rifle which fired the bullet that killed MLK.

Broached rifling can often be easy to identify as the metal which creates the rifling is actually cut away from the inside of the barrel. As the broach wears, and sometimes gets little nicks on the cutting surfaces, distinct marks are often created.

Button rifling on the other hand, is not easy to identify. In fact, it can be virtually impossible, for the following reasons.

Instead of cutting the metal away, button rifling compresses the metal.
As the rifling button doesn't have cutting surfaces to get dull or chip, it not only lasts longer, it gives more uniform results from barrel to barrel.
Furthermore, rifling buttons are considerably cheaper to produce than broaches. This makes them far less costly to replace.

Because button rifling gives more uniform results for considerably lower cost, the firearms industry is going to button rifling in a very big way . . . for both hand guns and rifles.

There is another rifling process used for custom match pistol barrels, but it's still quite rare. This process creates the rifling by eroding the metal away through an electro-carbon process, but I don't need to go into that right now.

Ken V.

In your story, are you trying to get a gun identified? Or are you trying to KEEP a gun from being identified?

Excellent question. (Wishing I had asked it that well.)

I would like to expand on your post if I may -- too late, I've already done it.

The rifling from the barrel of any gun will show up on a bullet. Even if two bullets are fired at two different people.
The only exceptions to this that I know are:
1. the weapon fired was a shotgun (no rifling exists in most shotguns...they spray little lead balls) or

2. the person uses a sabot round (most pistols don't fire sabot rounds...it's a rifle thang). A sabot is a false covering, such as paper or hard plastic, that falls away from a bullet after it exits a barrel. It imparts a spin to the bullet that maintains accuracy, but protects the bullet from getting marks on it.

Sabot means "shoe." And sabotted rounds are also extensively used with shotgun slugs. Sabots are generally used with rifled shotgun barrels -- although there are some smooth bore shotguns that have an optional rifled choke adaptor.
Shooting shot-loads out of a rifled shotgun barrel is a bad idea because the centripital force imparted by the spin sends the shot pattern wide almost immediately upon leaving the barrel. Ten feet or farther from the barrel, the shot pattern looks like a doughnut.

If the gun is an semi-automatic (or machine gun) then spent cartridge cases will litter the ground. From these, you have two identification points typically.

1. Firing pin marks on the shell
2. Extractor marks on the shell (scratches on the shell where the little thingy pulled the shell out of the barrel after you fired the gun.)

Also ejector marks, machine marks on the breech-face, and marks on the cartridge case wall left by the chambering reamer. All of which will change slightly from the build-up of powder residues as the gun is continually fired and not cleaned. Powder residues are also slightly abrasive, so a gun that is used a lot will show changes in the marks over time.

If one is trying to keep the gun from being identified, -- something that would take very little time for someone like me (if I were so inclined) -- polish the firing pin head, extractor, and ejector, (you could just sand them lightly with a fine sand paper) stone the breech-face, wrap some Scotch-Brite on a drill-bit and lightly polish the chamber, and finally, clean the bore with a stainless steel bore brush. (Those stainless brushes are very hard on a barrel.)
If I wanted to get REALLY elaborate, I could lap the bore, which would remove virtually ALL the minor scratches -- although changing the barrel would be quicker . . . especially on an auto-loader.

Ken V.

Thanks for the help, guys! Please feel free to continue at length. As I said, I am an ignoramus when it comes to these matters.

In the story it would only be important that the people who are shot be identified as being shot with the same gun. The person shooting them isn't trying to hide his identity.

Lisa

Thanks for the help, guys! Please feel free to continue at length. As I said, I am an ignoramus when it comes to these matters.

In the story it would only be important that the people who are shot be identified as being shot with the same gun. The person shooting them isn't trying to hide his identity.

Lisa

Rifle, or pistol?

Once we know that, we can come up with enough answers to confuse the hell out of you.

Ken V.

I was also told that it's a good idea to wipe cartridges before you load them to remove any fingerprint swirls that you might leave on the shells. Or buy a fresh box of bullets and wear rubber gloves while loading them. A revolver doesn't have this problem if you carry the bullets away with you, but a semi-auto can throw them all over the place.

Just write in your story that "The ballistics report came back, and it's a match. Same gun."

Which of course means that it was.....................Howard!!!!, the Bulgarian butler who immigrated to the US after so many years behind the Communist Steel Shade which caused him to lose his mind and began killing women for their farm vegetables.


______________________________________________________________
Never initiate force against another.That should be the underlying princi-
ple of your life. But should someone do violence to you, retaliate without
hesitation, without reservation, without quarter, until you are sure that he
will never wish to harm-or never be capable of harming-you or yours
again.
from THE SECOND BOOK OF KYFHO
(Revised Eastern Sect Edition)
From Enemy of the State by Some minor writer

I was also told that it's a good idea to wipe cartridges before you load them to remove any fingerprint swirls that you might leave on the shells. Or buy a fresh box of bullets and wear rubber gloves while loading them. A revolver doesn't have this problem if you carry the bullets away with you, but a semi-auto can throw them all over the place.

Cartridges are what you load into the gun. Bullets are what come out of the barrel. Brass -- or cartridge cases -- are what remain.

I'm kind of particular on the issue of proper nomenclature.

Minor example:

I was doing some ammunition testing on a customer's gun a few years ago, and wanted to change the lube on cast bullets he was using. (He had an OUTRAGEOUS leading problem.) I asked him for a couple hundred BULLETS . . . he sent me two hundred loaded CARTRIDGES. By the time I got what I asked for, and completed the testing, he had missed an important match.

______________________________________________________________
Never initiate force against another.That should be the underlying princi-
ple of your life. But should someone do violence to you, retaliate without
hesitation, without reservation, without quarter, until you are sure that he
will never wish to harm-or never be capable of harming-you or yours
again.
from THE SECOND BOOK OF KYFHO
(Revised Eastern Sect Edition)
From Enemy of the State by Some minor writer

Love that quote.

Ken V.