Re: Bullet Deflection due to sloped winsheild

Let me make sure I understand the question, you are saying a bullet is 
deflected upward when fired at a car’s windshield, right?  This is a good 
question that requires some thought and many different aspects to solve.  
First of all, it is proven, and we will discuss what factors makes this 
happen.  As you know there are many different Physics principles that come 
into play, one of them is the angle of incidence = the angle of reflection.

The scene; The shooter is on the ground in front of a car say 60 feet 
away.  He has a 38 caliber revolver, a 44 caliber revolver, and a SKS 
rifle.  For the 38 the suspect has hollowpoints, and also wadcutters 
bullets -which are flat on the end instead of round.  For the sake of this 
experiment let’s say the windshield has a 30 degree angle in relation to 
the hood of the car.  Which means the bullet will travel parallel to the 
ground (and hood)and it will strike the glass at 30 degree angle in 
relation to the glass. 

Now the factors that determine if the bullet will go through the 
windshield or be deflected upward are as follows: 1. The angle of the 
windshield in relation to the shooter on the ground, 2. The velocity and 
weight of the bullet being fired, 3. The hardness of the surface being 
shot, in this case the window- which is hard, and 4. The shape of the 
projectile.

All of these factors are variables and all work together, so it is hard 
for me to address them one at a time, but I will try.  If we start by 
knowing that a bullet will bounce off we can better explain the 
variables.  

1. If the shooter is not on the ground, but is on top of a building then 
the angle might be 80 degrees and would not deflect off but would pass 
through the windshield, keeping velocity, weight, and shape in mind.  
2. Slower velocity bullets such as a 22 caliber and the 38 caliber tend to 
deflect off because of velocity, hardness of the windshield, and angle,  
while the 44 caliber and the rifle will punch through the windshield 
because of the higher velocity, shape of the bullet, and or weight of the 
bullet.
3.  If the surface was not a windshield but a piece of plywood at the same 
angle, then the bullets might still deflect, this would take some 
experimentation.
4.  The shape of the projectile plays a role because the rifle bullet has 
a point that would tend to “cut” into the glass, the same would apply to 
the wadcutter and hollowpoint.  A roundnose bullet would tend to follow 
the curve of the windshield.

One other thing for you to think about is the fact that if a person is 
shooting at the police from under a car and the police are say 150 feet 
away they can shoot toward the (hard) blacktop (say 15 degree angle) and 
the bullets will deflect up at 15 degrees or less and basically travel 
along the ground and could possibly hit the shooter,
(angle of incidence = the angle of reflection).  This also works with 
walls.  The reason this works has to do with the factors mentioned above.  
As you can see your question gets pretty complex with  so many variables.  
An easy way to think of these principles is to think about skipping stones 
across the water.  By the way bullets will also skip if the angle is 
small.  Thanks for the question keep the challenging questions coming.