What energy do you need to take out windshields?

P

Pond James Pond

New member
Whilst I don't let such events affect my day to day decisions or political choices, the spate of car-based terrorist attacks in Europe have at least made me think about my own actions in that situation.

In all the cases that I can think of, the attacker behind the wheel was eventually stopped with bullets. (although in London this week, he had left the vehicle by the time he was stopped by armed police)

So I ask myself, assuming the standard angle of impact from a grown person aiming at a driven vehicle's windshield, what sort of KE would you need and what sort of bullet?

I ask about KE rather than calibre because a 9mm from a short barrel may not have the KE of a .38Spl from a long barrel etc...

For example, I have a 2" .38Spl and I doubt I could penetrate a windshield with that if someone where driving at me or mine...
 
James,

No, your snub-nose .38 special will most likely not go through that tough piece of curved plexy glass!

More than one NATO 9mm, from a 4" plus barrel, more of a chance. Mind you, a dead driver is not a vehicle stopper you know! In the case of the British Born Muslim? On the Bridge in London UK, he would have not been able to have gone from his SUV, if he had been dead, still in vehicle?

The Un-armed Officer in the Building (a disgrace from our backward Police in the UK!) stabbed to death. A Glock 17, with a secure holster? It is the easiest firearm to carry, and to train to use. If each Police Officer in that Building was armed, with just a pistol. Not all swatted up, probably with 20 lbs of gear.

Chances of survival would have been much better, for all.
 
I have some military issue(European?) purported to be "antiskid, glass penetrative". It has a slightly hollow nose with a very sharp edge. When first acquired, I tried it on some angling shots at auto glass and car bodies. No skittering visible even at 45* angle to glass.
The bullet nose is more important than the cartridge or delivery tool.
 
Windshields are constructed much stronger than other windows . To rescue people from a car don't try the windshield , side windows are much easier ! While here at least armor piercing bullets are restricted to police, the best for civilians is the all copper Barnes type bullets which can even expand after going through sheet metal like side doors. BTW doors have become reinforced for side impact !!
Here the training is to stop the driver . not the car , much easier.
 
I was a sniper instructor (both LE and Military)

I'd get junkyards to donate windshields and other glass to demonstrate just what happens when you shoot windshields.

Just about any modern cart. (including 38s) will penetrate a normal windshield. Just about any cartridge could be deflected to a point while going through the windshield.

More importantly we discovered no two same bullets will react the same way going through windshields.

When shot, you get a hole in a windshield, (normally) lots of cracked glass but the windshield stays in place. Side windows shatter (normally).

You'll see a lot of "normally" in my post, that's because as I mentioned, no two similar bullets, shot the same distance and as close as possible at the same angle. will react the same way.

The same can be said for windows in houses and stores.

Want to get really confused. Get a good study one what happens shooting double pain windows. Then, introduce triple pain glass which makes good windows in in cold climates like Alaska where I was in LE.
 
It's more about the bullet's shape and construction. One of the police complaints about the .38 Special, away back when, was it's lead RN bullet would bounce off most car windshields. The SWC's subsequently adopted weren't much better. So they said at the time. Mind you, most cops have a hard time hitting a windshield with anything.
"...a dead driver is not a vehicle stopper..." Neither is any other cartridge's bullet. Nothing will stop a car in its tracks. Physics doesn't allow it. Shoot the driver and you have an uncontrolled, approximately 1 ton, projectile.
Anyway, windshield glass is tempered so it will not shatter into sharp shards. It's part of the vehicle's structural integrity. Taking one out doesn't accomplish anything.
 
I have no experience or expertise on this subject, but I believe (or assume) the angle at which the projectile hits the glass will have a significant effect up on the path of the projectile from the instant it strikes the glass and the resulting impact on the glass.
 
All the glass in cars, in the USA, are tempered glass. The front and rear glass are two sheets laminated together to keep it in place. The tempered glass cracks and breaks into small pieces to prevent large shards of glass that can kill. The plastic lamination in the front and rear glass holds the sheets together when it is broken. I have shattered a car windshield with a single shot from a BB gun. (.17 caliber) at an angle of approximately 20 degrees (90 degrees being straight at it). The BB did not penetrate the glass and was not recovered.
Penetrating the glass and injuring the operator could be done with a 380 auto at a few yards but glass and the layer of plastic film would hamper the accuracy and the terminal ballistics.
 
Although I did not mention in my post, the angle at which the projectile strikes the glass also includes the angle, i.e., slope, of the windshield. For example, a bus windshield is nearly vertical but a sports car windshield may have a very low slope.
 
All the glass in cars, in the USA, are tempered glass. The front and rear glass are two sheets laminated together to keep it in place. The tempered glass cracks and breaks into small pieces to prevent large shards of glass that can kill. The plastic lamination in the front and rear glass holds the sheets together when it is broken. I have shattered a car windshield with a single shot from a BB gun. (.17 caliber) at an angle of approximately 20 degrees (90 degrees being straight at it). The BB did not penetrate the glass and was not recovered.
Penetrating the glass and injuring the operator could be done with a 380 auto at a few yards but glass and the layer of plastic film would hamper the accuracy and the terminal ballistics.
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No. The windshield is laminated glass in a car and it will crack and tempered glass will not. The rest of the glass in the car, including the rear glass is tempered glass. Tempered glass will not crack but it shatters into small glass gravel to keep it from cutting anyone. Back in the "good old days" prior to the late 50s, all of the glass in cars was laminated and you frequently found cracks in the door and side glasses. Back in my youth and before they started curving the side glass, we would find a larger glass in an old junked car and cut it to fit a smaller opening. You can cut laminated glass with a glass cutter but you cannot cut tempered glass. My first experience with tempered glass was in the early 60s. I was working on a 1957 Chevrolet and I had laid a wrench on the trunk lid. I opened the trunk which caused the wrench slide and hit the glass on a hot day and the rear glass exploded into many small pieces.
 
tough piece of curved plexy glass!
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No such thing on automobiles. Laminated yes; plastic, no

With some cars having severely angled windshields for less wind resistance and better gas mileage, your best bet would be a side shot at the driver's window
 
All you need to do to break tempered glass is to scratch it. You can beat on it all day long with heavy hammers and it won't break, but use something hard to scratch it and it explodes into thousands of pieces. Steel BB's from BB guns are notoriously effective at breaking them. Some thieves use a piece of broken spark plug porcelain on the end of a string to break tempered glass.

Tempered glass is cooled in a way that leaves the core under tension while the surface is under compression. That compressed surface makes it hard for cracks to get a place to start, that's why its so hard to break. But if the core under tension is compromised, cracks will spread throughout the core almost instantly turning the entire piece of glass into glass gravel.
 
I would say a .357 out of a 4'' barrel would be about the minimum to go trough the glass and reliably take out a threat. My $.02
 
Windshields are very unpredictable. They're quite tough and are angled. I'm pretty sure I'd focus on getting as far out of the way as possible if one was coming my way. How do you know if its Joe terrorist or runaway grandpa coming at you?
 
Please don't forget at least one of these type attacks(possibly more, just don't know) was committed in a truck. That introduces a whole new set of dynamics. Truck windshields are thicker and made to last longer than standard cars. They also need to be made thicker because of the greater expanse of area they cover. Over 6 ft.in some instances. That plus the difference in firing at them at an upward angle changes things. A caliber that will take out a car window probably won't do it on a truck. Gonna take a rifle round, and like someone said , a dead driver doesn't mean the vehicle is gonna stop. Think of the gross weight and increased size and mass of a truck (lorry)
 
What you folks need to do is actually test different rounds on a windshield.
I have fired a 380 95grain bullet from 21 feet through a windshield with a sheet of 3/4" plywood 2 feet behind it and penetrated both from 45 degrees with no noticeable deflection of the bullets path. It doesn't take a 357 or a 45 to penetrate a piece of safety glass and a person behind it, well unless it is armored glass.
 
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