Quantified Bullet Deflection vs Windshields

[marksman1023]

I've been chewing through this forum page for quite a while, and it's been very informative - especially getting to read such a wide variety of actual test data.

My primary question concerns actual deflection of projectiles versus auto windshields. I'm familiar with the arguments that nine millimeter hollowpoint ammo deflects "badly" versus auto windshields...this is one reason I chose the Ranger RA9TA over faster 115gr loadings as my carry ammo. However, I've yet to find/google/browse through something that actually quantifies "bad deflection."

What's most common? Are we talking a deflection of a few degrees, resulting in a few inches POI/POA difference, or are we talking a major deflection that would cause a miss on a standard human target? In almost everything I've seen it's a nebulous statement.

Also, what's the difference between 9mm, .40, and .45 on this? I have a hard time believing any of the above just lasers through a modern auto windshield with zero deflection.

My chosen loads are the Ranger SXT RA9TA, 127gr +P+, and the Speer Gold Dot 124gr for my dad's aging Smith & Wesson 59's as he is concerned about beating them to death with +P and +P+ ammunition. Any data on these would be appreciated, especially as they compare in terms of deflection as compared to 165gr/180gr .40 S&W loadings.

On this forum I've seen some of the most detailed and thorough information on terminal performance I've ever come across, so I'm hoping you guys can help me out.

[481]

My primary question concerns actual deflection of projectiles versus auto windshields. I'm familiar with the arguments that nine millimeter hollowpoint ammo deflects "badly" versus auto windshields...this is one reason I chose the Ranger RA9TA over faster 115gr loadings as my carry ammo. However, I've yet to find/google/browse through something that actually quantifies "bad deflection."

I think that what you are describing is a pretty tall order due to the highly variable geometry (of both windshields and engagements/presentations) and the large scope of difference in the materials involved. I am not saying that it cannot be done- just that it will require an immense data base from which to draw a valid conclusion.

[S. Galbraith]

Defeating a windshield and minimizing deflection is more about bullet durability rather than caliber size. Generally, larger, heavier bullets tend to hold up better when punching through a windshield. More mass, thicker nose area, and thicker jackets and more durable expansion petals. However, in recent years, modern bullet designs have made smaller caliber bullets more durable. In the 1980s and early 1990s, 9mm and .38spl bullet designs shed too much of their mass and did not do too well against windshields. Thus, the FBI opted to go with the 10mm and later the .40S&W.

Today, designs like the Speer Gold Dot, Winchester Ranger Bonded, Federal Tactical Bonded, and Federal HST are more durable than those 1980s designs. So, in 9mm and .38spl they actually do pretty well against windshields. The larger calibers like .40S&W tend to do a little better. An easy test to compare calibers is to shoot into frozen jugs of water since it is a hydraulic substance that makes a JHP fully expand, but the hardness of it really stresses the bullet. .40 and .45 JHPs in most brands will expand fully while retaining almost all of their bullet mass. 9mm loads usually shed quite a bit of their mass in the ice though since their expanded petals are more fragile. However, but the modern day 9mm works pretty well in the field at least.

Bullet sectional density is also an important characteristic of good penetration through tissue and barriers:
http://www.firearmstactical.com/tact...umber1/toc.htm
Generally 9mm 147gr, .40S&W 180gr, and .45acp 230gr tend to have the best all around penetration characteristics.

[WS6]

Having shot from inside of vehicles out of them, and out of them into them, I feel confident in saying that you will not find what you are after. When shooting into a vehicle, fire for effect aiming COM and you should hit your target, provided your ammunition will hold together.

Firing out of a vehicle, make a hole and insert the rifle barrel through it, or shoot a hole and aim the pistol through it. Jamming the muzzle of a semi-auto through the windshield will likely result in a jam if the slide interacts with the windshield. Shooting through glass from inside of a vehicle, you won't hit anything but by luck---good or bad.

Side windows are gone after the first shot or two, sacrificial round and then fire for effect.

[Moltke]

You can think of "bad deflection" as when the projectile has deviated from it's direction of travel enough to not hit the target either because it 1) failed to penetrate the barrier or 2) failed to remain on course after penetrating the barrier.

Quantifying "bad deflection" beyond that simple definition would be difficult but it could be done with enough testing and actively shooting through windshields. Windshield properties would have to be catalogued and would need to include angle/thickness/temp/age/material/etc - and I just don't see that happening.

It generally comes down to "is the juice worth the squeeze?" What large sum of money is going to be spent to discover what small amount of information? I think what DocGKR has shown us already is good enough for us as consumers, LE, or otherwise to make informed decisions on what types of ammo we are carrying and using on a daily basis. Pick something from his list that will fit your needs and move on to focus on training - don't chase the minutia.

[kmrtnsn]

Too many variables. Glass angle, position on the pane or panel, temperature, aftermarket films, all can affect bullet performance through auto glass.