OK I have a question about rifling... no so much shooting related.

[joshua99ta]

I doubt this IS the proper place for this BUT it does say barrels! lol

I keep seeing all of this here info on TV about ballistics testing on these murder shows and stuff. They take a certain gun and match the rifling on a bullet recovered from a body and then take the supposed gun and fire a round and then match the rifling.

NOW my question is that if a barrel is made with any sort of quality control shouldn't ALL of the riflings MATCH IDENTICALLY??

I mean if you take 2 remington 700 barrels produced on the same day one after another with the same tooling it looks like to me that a bullet fired from each should match exactly?!?

 

[4bycamper]

Good question. Who would know the answer??

So, in my best guess: OK, the 2 rifles you mentioned would be very similar but what's the odds of the two owners being in the same place ( the crime scene ) at the exact same time? I think the prosecutor still needs to place the defendant at the crime scene to make a conviction stick.

JM .02

 

[joshua99ta]

this just kind of bumfuzzles me how supposedly they can prove that a bullet came from a certain barrel when there are thousands a day produced.

I mean I know the chances of somebody else could have a rifle with the same tooling and it be in the same place arent likely but I doubt mass produced barrels have different toolings for every barrel.

 

[Michael Eichele]

That is like saying there are 7 billion people in the world therefore 100,000 people must have the same DNA.

The fact is that no 2 peices of steel are the same. They will react differently to the tooling being used. Tooling wears with every barrel it passes through and will be micrscopically different each time it makes a barrel. Some barrels are lapped. There is no way 2 barrels could be lapped the exact same way. Shooting and cleaning alters the barrel as well. There is no way that microscopically, 2 barrels are equal. This is why they call it 'fine striations' It takes a micro scope to see these differences. There are simply too many variables to make barrels have the exact same fine striations.

 

[elkaholic]

That is like saying there are 7 billion people in the world therefore 100,000 people must have the same DNA.

The fact is that no 2 peices of steel are the same. They will react differently to the tooling being used. Tooling wears with every barrel it passes through and will be micrscopically different each time it makes a barrel. Some barrels are lapped. There is no way 2 barrels could be lapped the exact same way. Shooting and cleaning alters the barrel as well. There is no way that microscopically, 2 barrels are equal. This is why they call it 'fine striations' It takes a micro scope to see these differences. There are simply too many variables to make barrels have the exact same fine striations.

Agree with Michael.....Rich

 

[dogdinger]

Think of them as the "fingerprints " of the rifle......no two are the same. if a bullet is recovered in decent shape it is about 99% that it can be matched to the gun, providing the gun is available and has not been altered. I watched a whodunit the other night where the perp killed a lady with a .45 auto, then ran a drill bit down the barrel and made it a smoothbore......but.....the investigators dug old bullets out of a dirtbank where he had been shooting and matched them to the bullets recovered from the body....busted!...AJ

 

[Topshot]

The smart crook will after the crime, put a bit of lapping compound and sand grit on a cleaning patch and run it through his barrel a few times.

Shazzam, the barrel has a different finger print and the perfect crime has been committed.

That is until they find the patch with grit and paste! Not thinking of doing this are you?

 

[Michael Eichele]

The smart crook will after the crime, put a bit of lapping compound and sand grit on a cleaning patch and run it through his barrel a few times.

Shazzam, the barrel has a different finger print and the perfect crime has been committed.

That is until they find the patch with grit and paste! Not thinking of doing this are you?

Forensic analyzers can also take spent cases and match the tooling marks impinted on the primer and case base. Even with a new barrel or modified barrel they can still match a case to an action. Not so much an issue for revolvers and bolt guns but can be problomatic with semi-autos when cases are flying every which way.

 

[elkaholic]

Did you guys all belong to the Mafia?

 

[Topshot]

No, just smarter that the average bear Bo Bo.

 

[joshua99ta]

lol topshot... no im not thinking about it... I just like watching csi, and ncis and shows like that. Not the killer type myself. Definately not one where it would be anything other than self defense!

 

[Fitch]

this just kind of bumfuzzles me how supposedly they can prove that a bullet came from a certain barrel when there are thousands a day produced.

I mean I know the chances of somebody else could have a rifle with the same tooling and it be in the same place arent likely but I doubt mass produced barrels have different toolings for every barrel.

They certainly look different, even to the eye in a borescope. Also, the usage histories of the rifles will be different probably beginning with the first shot. Different break in, different cleaning, different bullets, plus the initial differences just in chambering tolerances (which are pretty wide in factory guns) and there is essentially zero chance the scratches on the bullets or cases will be identical.

Trust me on this, based on years of looking for root cause failures in silicon chips it is really hard to make things as gross as a barrel identical at a microscopic level on purpose, never mind by accident.

Fitch