What Happens to Bullets When They Hit Auto Glass?

[revchuck38]

Specifically, what happens to their trajectory? If it hits at an angle, does it deflect as a result, e.g., does a bullet fired at a windshield deflect upward? I'm not planning on shooting any cars, just wondering in case some knucklehead is running people over and I'm in the way.

[4RNR]

Many videos on YouTube. Many go straight through

Sent from my moto z4 using Tapatalk

[WobblyPossum]

Rounds that do well in the FBI gel testing protocols should penetrate the windshield glass while retaining most of their mass and still be able to reach the vitals of a person. There is an auto-glass stage to the testing protocol. My understanding is that bullets that penetrate the windshield from outside of the vehicle deflect downwards a little. One of my coworkers got into a shooting in which he fired through a windshield and, based on where he was aiming, the bullet did deflect downwards and impacted lower than the POA.

[Lon]

I’ve done a lot of training in and around vehicles. Quite often shooting through windshields is like a box of chocolates. But generally speaking with a lot of caveats, outside/in goes downward and inside/out goes upward. The exact amount of deflection changes depending on a variety of factors.

[Joe Mac]

I’ve done a lot of training in and around vehicles. Quite often shooting through windshields is like a box of chocolates. But generally speaking with a lot of caveats, outside/in goes downward and inside/out goes upward. The exact amount of deflection changes depending on a variety of factors.

This, precisely.. In general, bullets fired through a windshield (into the car) will usually deflect downward by several inches, because the bottom of your bullet nose is hitting the angled glass first, tilting it downward as it penetrates.

[vcdgrips]

Story of one. Training with a regional FBI SWAT team.

Mid 80s Lumina. 62 g bonded HP thru a 10 or 11 inch AR at 50 yrds with an Aimpoint. IIRC braced on a backpack on a platform to simulate to top of a car.

I held just above the top of the T-Box on a "face target" and it dropped it in just below dead center. Maybe a 3 inch drop at 50.

Also confirmed that day that a 7 or 8 year old Body armor that had been in the back of a truck of a supervisor's car for the entirety of its life still exceeded it rating with multiple hits.

[TiroFijo]

I’ve done a lot of training in and around vehicles. Quite often shooting through windshields is like a box of chocolates. But generally speaking with a lot of caveats, outside/in goes downward and inside/out goes upward. The exact amount of deflection changes depending on a variety of factors.

This is the general rule... in the vertical plane.

https://i0.wp.com/www.tactical-life.com/wp-content/uploads/sites/8/2016/08/gwjj16-glass-graphic.jpg?zoom=2&resize=150%2C150&ssl=1

[LtDave]

From personal exprience, 1990 vintage Winchester 147 OTM will deflect off side window glass of a 1991 Chevy Caprice. Multiple times.
Will penetrate rear window.

[the Schwartz]

This is the general rule... in the vertical plane.

https://i0.wp.com/www.tactical-life.com/wp-content/uploads/sites/8/2016/08/gwjj16-glass-graphic.jpg?zoom=2&resize=150%2C150&ssl=1

That diagram is also correct for the horizontal plane as addressed in numerous papers by Alekseevskii and Tate and their contemporaries regarding the behavior of yawed impactors in targets (e.g., sloped armor).

[RevolverRob]

That diagram is also correct for the horizontal plane as addressed in numerous papers by Alekseevskii and Tate and their contemporaries regarding the behavior of yawed impactors in targets (e.g., sloped armor).

I'll admit, it took me way too long to understand the WHY behind this.

But I finally realized it's basically a function of "braking". The part of the bullet that hits first is suddenly and rather abruptly slowed down. Causing the bullet to yaw in the direction of the braking. Now I see how larger caliber/higher mass bullets can help mitigate this problem a bit. And how bonded and monolithic rounds avoid the secondary problems of the jacket shearing off or beginning to flatten/mushroom.

I failed kinematics twice in college, but physics is pretty cool. Still prefer electricity, light, and magnetism though (I made an A in that course...).

[Hambo]

I’ve done a lot of training in and around vehicles. Quite often shooting through windshields is like a box of chocolates. But generally speaking with a lot of caveats, outside/in goes downward and inside/out goes upward. The exact amount of deflection changes depending on a variety of factors.

Same here; same story. Training ammo would deflect the same, get shredded sometimes (or not depending on caliber), sometimes the core still hit the target.

[the Schwartz]

I'll admit, it took me way too long to understand the WHY behind this.

But I finally realized it's basically a function of "braking". The part of the bullet that hits first is suddenly and rather abruptly slowed down. Causing the bullet to yaw in the direction of the braking. Now I see how larger caliber/higher mass bullets can help mitigate this problem a bit. And how bonded and monolithic rounds avoid the secondary problems of the jacket shearing off or beginning to flatten/mushroom.

I failed kinematics twice in college, but physics is pretty cool. Still prefer electricity, light, and magnetism though (I made an A in that course...).

Your explanation is a pretty good one for someone who admits to having struggled with kinematics.

The turning moment, more correctly defined as ''moment of force'', induced by the asymmetric contact projectile/target interface is dependent upon the angle of the impact face. There is also a critical angle, ß, at which the projectile cannot overcome the dynamic strength, RT, of the target being struck which results in the projectile being fully deflected (ricochet) from the target face, failing to defeat it.

In the AT model, Tate (of Alekseeskii and Tate) computes the deflection vector as being perpendicular to the axis of the rod multiplied by one-half the length of the rod, to obtain the moment of force about the projectile's center of gravity. This moment induces a longitudinal rotation in the projectile body—which is treated as being rigid—that results in the critical ricochet condition.

94235

In later work, Rosenberg et al. go about the process of determining the critical deflection angle differently. In their approach, the asymmetric force assumed in Tate’s model is assumed to act only upon the mass located at the tip of the projectile which is engaged by direct contact at the nose-target interface. This alteration was made in order to account for the plastic hinge that occurs as the forward portion of the rod bends during its deflection from the target face. Rosenberg's model is also dependent upon the dynamic target strength, RT, which is velocity-dependent in that as impact velocity increases RT decreases, which requires iterative computational steps to correctly represent the extent of the elastic-plastic zone formed in the target ahead of the projectile's nose.

94236

ETA: in the equations cited above, U is velocity of the projectile's nose at the point of contact with the target and V is the projectile's impact velocity.

[farscott]

The (V+U)/(V-U) ratio also shows up in the reflection coefficient for electromagnetic waves when the impedance of the medium changes. The models are remarkably similar.

[the Schwartz]

The (V+U)/(V-U) ratio also shows up in the reflection coefficient for electromagnetic waves when the impedance of the medium changes. The models are remarkably similar.

Yep. It does. I'll be damned!

Just as the speed of light decreases in mediums denser than air, so too does the velocity of the nose of a penetrator when it strikes a target medium.

As you might expect, the value of U (penetration velocity) is related to the ratio of the density of the projectile and target material as in this equation—

94244

It is amazing that two phenomena (electromagnetic waves and non-linear impact response mechanics) so different from one another could have such commonality.




Although I prefer the Rosenberg methodology over the AT model's methodology for the determination of a target-projectile pair's critical angle, solving for RT—

94245

is where the real difficulty exists since it requires αp be determined iteratively through the solution of the following transcendental equation—

94246

[LockedBreech]

Y'all are going full Good Will Hunting and I'm still sitting here murmuring "inside up, outside down" to try and memorize it.

[Hambo]

Y'all are going full Good Will Hunting and I'm still sitting here murmuring "inside up, outside down" to try and memorize it.

C'mon, man. If you can't run those numbers like Rainman in a gunfight, you're dead in the streetz. ;)

[PrideAmmunitionComponents]

I’ve done a lot of training in and around vehicles. Quite often shooting through windshields is like a box of chocolates. But generally speaking with a lot of caveats, outside/in goes downward and inside/out goes upward. The exact amount of deflection changes depending on a variety of factors.

I've heard the same exact thing from many combat veterans. That's right on the money.

[blues]

transcendental equation

https://groovyhistory.com/content/205085/a6ccc982e5524315a795bb95dd208d51.jpg

"Wait...did I carry the nine or...? My mind's a blank."

[the Schwartz]

Transcendental equations are no big deal.

The trick is to find the value(s) of the variable being investigated that satisfies both sides of the equation.

So, for example, look at the simple linear transcendental equation 2a = a + 1

We just graph the two sides of the equation after we set each side to 0.

94257

Where both lines intersect, we get the solution of a = 1.



Or, we can do it ''by hand''...

2a = a + 1

Solve for 'a'

2a - a = (a - a) + 1

Eliminating excess terms, we get...

a = (a - a) + 1

a = 0 + 1

a = 1

Substituting

2a = a + 1 where a = 1

2 x 1 = 1 + 1

2 = 2




ETA: For anyone with the burning desire to know the solution for the transcendental equation in post #14, it is—

94264

[Half Moon]

Y'all are going full Good Will Hunting and I'm still sitting here murmuring "inside up, outside down" to try and memorize it.

94263

[medmo]

Your explanation is a pretty good one for someone who admits to having struggled with kinematics.

The turning moment, more correctly defined as ''moment of force'', induced by the asymmetric contact projectile/target interface is dependent upon the angle of the impact face. There is also a critical angle, ß, at which the projectile cannot overcome the dynamic strength, RT, of the target being struck which results in the projectile being fully deflected (ricochet) from the target face, failing to defeat it.

In the AT model, Tate (of Alekseeskii and Tate) computes the deflection vector as being perpendicular to the axis of the rod multiplied by one-half the length of the rod, to obtain the moment of force about the projectile's center of gravity. This moment induces a longitudinal rotation in the projectile body—which is treated as being rigid—that results in the critical ricochet condition.

94235

In later work, Rosenberg et al. go about the process of determining the critical deflection angle differently. In their approach, the asymmetric force assumed in Tate’s model is assumed to act only upon the mass located at the tip of the projectile which is engaged by direct contact at the nose-target interface. This alteration was made in order to account for the plastic hinge that occurs as the forward portion of the rod bends during its deflection from the target face. Rosenberg's model is also dependent upon the dynamic target strength, RT, which is velocity-dependent in that as impact velocity increases RT decreases, which requires iterative computational steps to correctly represent the extent of the elastic-plastic zone formed in the target ahead of the projectile's nose.

94236

ETA: in the equations cited above, U is velocity of the projectile's nose at the point of contact with the target and V is the projectile's impact velocity.

I love this kind of shit. Thanks. I could polish off a big box of Crayolas reading through it. Very entertaining. "elastic-plastic zone, computes the deflection vector, forward portion of the rod bends...." Love it!
:)

[the Schwartz]

I love this kind of shit. Thanks. I could polish off a big box of Crayolas reading through it. Very entertaining. "elastic-plastic zone, computes the deflection vector, forward portion of the rod bends...." Love it!
:)

Mmm, Mmm, Mmm...Crayola Crayons are my favorite....'specially the ''purpley'' ones. ;)

[blues]

You kids are dead after school...

[willie]

Schwartz could be making all this shit up, and we wouldn't know better. I did ok in algebra, but by the time I figured out what X was, then they slipped a Y in on me.

[the Schwartz]

Schwartz could be making all this shit up, and we wouldn't know better. I did ok in algebra, but by the time I figured out what X was, then they slipped a Y in on me.

We may never know... :cool:


https://www.youtube.com/watch?app=desktop&v=jEILGYq7eso

[CCT125US]

Y'all are going full Good Will Hunting and I'm still sitting here murmuring "inside up, outside down" to try and memorize it.

An easy visualization that is working for me... what part of the the bullet contacts first? Up, down, left or right? That is the angle of deflection.

Not to be confused with up, up, down, down, left, right, left, right, B, A, select, start. Totally different.

[LockedBreech]

An easy visualization that is working for me... what part of the the bullet contacts first? Up, down, left or right? That is the angle of deflection.

Not to be confused with up, up, down, down, left, right, left, right, B, A, select, start. Totally different.

Hahah hey I get that reference!

[blues]

I think of it like this...

Shooting from outside in gives a better chance of shooting someone in the dick.

Inside out...a better chance of a head shot.

(Just a gross generalization to remember which is which. Toward the "Sky or Thigh".)

[Beat Trash]

I think of it like this...

Shooting from outside in gives a better chance of shooting someone in the dick.

Inside out...a better chance of a head shot.

(Just a gross generalization to remember which is which. Toward the "Sky or Thigh".)

Either of which should get someone's attention...

[willie]

I think of it like this...

Shooting from outside in gives a better chance of shooting someone in the dick.

Inside out...a better chance of a head shot.

(Just a gross generalization to remember which is which. Toward the "Sky or Thigh".)

Can you draw us a picture?:cool:

[blues]

Can you draw us a picture?:cool:

Have you got a magnifying glass?

[DMCutter]

I failed kinematics twice in college, but physics is pretty cool. Still prefer electricity, light, and magnetism though (I made an A in that course...).

This is why I'm a civil engineer. Everything I deal with is standing still. Electricity, magnetism, thermo, optics (Physics 251) was a 5 credit hour D for me...at the end of the semester I took the Halliday and Resnick textbook to a friend's farm and shot the shit out of it with my AR-180. I don't remember which way the bullets deflected.

[TCinVA]

https://youtu.be/TwXYEZC_Ocw

[Totem Polar]

Bullets and cars are interesting to me. I know for a fact (from a Matt Graham class) that the headrest in a 90’s accord will stop all common service calibers—an interesting tidbit.

I also took a “ballistics” course (which included shooting car parts with pretty much everything under the sun, from .380 to .308) from LE in N Idaho that convinced me that 12 gauge slugs are the way to go if one absolutely must shoot at something inside a passenger car.

And that’s all this musician has to add to this fascinating topic. I mean, aside from confirming that my own first shot through fresh windshield glass from the inside did go a little bit high, while the rest went through the created port to get on target per usual.