View Full Version : 9mm and auto glass
I have heard it implied that 9mm does poorly when shot through auto glass (especially when compared to .40). On the contrary, numbers that I have found on this forum seem to indicate that it performs decently:
Ranger:
9mm 147gr(990fps): (Penetration/Expansion)
Bare Gel: 13.9”/.65”
Through Denim: 14.5”/.66”
Through Auto Glass: 10.8”/.52”
.40S&W 180gr(990fps): (Penetration/Expansion)
Bare Gel: 13.6”/.71”
Through Denim: 13.9”/.68”
Through Auto Glass: 12.3”/.60”
Gold Dot:
9mm+P 124gr(1220fps)BONDED: (Penetration/Expansion)
Bare Gel: 12.7”/.67”
Through Denim: 18.2”/.55”
Through Auto Glass: 11.5”/.53”
.40S&W 180gr(1025fps)BONDED: (Penetration/Expansion)
Bare Gel: 14.2”/.68”
Through Denim: 18.1”/.59”
Through Auto Glass: 13.8”/.63”
HST:
9mm Fed 147 gr JHP HST (P9HST2) from G17:
BG: vel=1037f/s, pen=11.9”, RD=0.64”, RW=147.8gr
4 layer denim: vel=1049f/s, pen=14.7”, RD=0.54”, RW=147.5gr
auto windshield: vel=1042 f/s, pen=13.4”, RD=0.53”, RW=140.4gr
.40 S&W Fed 180 gr JHP HST (P40HST1) from S&W 4006
BG: vel=960 f/s, pen=12.6”, RD=0.65”, RW=181.1gr
4 layer denim: vel=961 f/s, pen=15.6”, RD=0.62, 181.3 gr
auto windshield: vel=904 f/s, pen=15.2”, RD=0.47”, RW=180.4gr
I was wondering whether there is more to it.
Is the 9mm significantly more likely to be deflected off course by a windshield than the higher momentum .40/.45?
Does the 9mm frequently fail to penetrate more than 7 inches or so into the gelatin (such as occurred in several of the ATK wound ballistics workshops http://le.atk.com/general/irl/woundballistics.aspx) whereas the numbers above represent a small sample size or best case scenario?
Is it that the larger and heavier rounds retain more mass and therefore can penetrate farther if jacket separation occurs (which I understand happens fairly frequently when auto glass is involved)?
Or is it simply that the 9mm rounds are at a very marginal disadvantage because they don't open up quite as robustly or consistently penetrate to exactly the 12 inch benchmark?
Thanks in advance.
9 mm can offer greater deflection, higher likelihood of deficient penetration after glass, more chance of marginal performance. Having said that, I have no problems carrying a 9 mm with good ammo...
citizensoldier16
08-17-09, 01:53
Given a CCW situation in the US, I think this is a moot point.
Situation 1: You're outside the car.
Assuming you are firing from a defensive range (read 10m or less) the deflection caused by glass is not enough to cause the round not to strike its target. Instead of hitting the 3rd rib, you might hit the 4th. Either way, dead assailant. Nobody expects surgical accuracy out of a 9mm pistol, especially a CCW gun, no matter what brand.
Situation 2: You're in the car.
Hit the gas and get the heck out of there. Use the car as both a defensive and offensive tool. Car won't start? GET OUT. Once out, problem solved...ie, no more glass b/t you and Mr. Bad Guy.
What I'm saying is that for CCW purposes, we really shouldn't be worried about a few grains of fragmentation or half a degree of deflection when firing any round through auto glass. What is lost by deflection can be regained by firing a few additional rounds at the assailant. Hey, you're carrying a 9mm anyway. You've got 15 rounds instead of a lousy 8 with a 1911. Use 'em! ;)
Assuming you are firing from a defensive range (read 10m or less) the deflection caused by glass is not enough to cause the round not to strike its target. Instead of hitting the 3rd rib, you might hit the 4th. Either way, dead assailant. Nobody expects surgical accuracy out of a 9mm pistol, especially a CCW gun, no matter what brand.
I'm not disagreeing carte blanche at all, but just to add to the discussion: I saw one of those tacticool shows on the outdoor channel (I know probably not the best source of info, but take it for what its worth), and they fired a handgun, I believe it was 9mm, from inside the car through the front windshield at a target that must have been no more than 5 meters away, and the round totally missed the man sized silhouette, it deflected that badly.
PA PATRIOT
08-17-09, 13:40
This is one subject I can chime in on, here in Philly we had a female officer who had to shot Thur her own patrol vehicle windshield at a bad guy who was armed and pointing a gun at her. From what I was able to learn about the incident the officer failed to make any hits and the shooting distance was from the drivers seat to the front bumper of the vehicle. I have a feeling after the first shot the windshield cracked/splintered the glass and that obstruct her vision.
So with that said there was a old non running Chevy sitting on a friends farm which had its windows intact. Now every model of car or truck has its own angle/shape of windshield and while I'm not sure I would say the base thickness of the glass must also vary. But what we did was move that Chevy to a safe firing location and placed B-27 style targets at three feet from the drivers side window were the height of the target would be roughly a man of 5 foot 10 inches. Now the drivers side door glass is mostly straight up and down so I would figure only my own shooting angle and not the angle of the door glass would factor in.
Since safety was are #1 issue we used a ballistic helmet with eye wear, ear protection and a very heavy duct tarp folded over four times and the shooter was wearing a ballistic vest.
Since we were shooting in such close quarters the shooter was allowed to lean to the right while seated to give about 16 inches of distance between the pistol and the glass. Lastly to stop flinching the magazine was load with eight dummy rounds and one live round in a unknown order to the shooter so the observer could see if the shooter was pulling the shot. I was the first shooter and the 9mm was a Glock Model-17 with Federal Classic 115gr standard pressure hollow points.
My first three pulls of the trigger were dummies and I was seen flinching on the first pull of the trigger. I aimed center mass on the forth shot when the pistol fired. The first thing I noticed is that the drivers window completely spider-ed obstructing all view. My shot hit the 9 ring and a piece a bullet jacket was seen laying on the ground in front of the target. I reloaded and fired three more shots Thur the same window and the spider-ed glass just dropped out of the frame and onto the ground. All shots hit the inside the 8-9 ring.
Now I have not researched this but side glass in a vehicle maybe different then windshield glass from what I have been told. Side glass is made to spider and drop out were windshield glass holds together to stop impacts from coming Thur to the driver.
Any how we set up for a windshield shot and placed the target right ahead of the drivers side headlight. This time five live rounds were used and after the first round was fired 50% of my vision to the target was obstructed. So the next four rapid fire rounds were my best guess of center mass and the results were not so good. I made three hits out of five and two of the hits looked as if they key holed the target. My friend watching from the rear outside of the vehicle stated the first shot hit the 9 ring, the second hit in the left shoulder and key holed, the third shot missed, the forth shot missed and the last hit the neck of the target and key holed. The holes Thur the windshield was all inside a area that I would say no more then three inches round.
We repeated the drill on the passenger side and my friend who is left handed missed four of the five shots Thur the front windshield passenger side with only his first shot Thur a unbroken windshield hitting low bottom 8 ring of the target and his hit did not appear to keyhole. We did find some small jacket fragments on the hood of the car and we did not recover any bullets. The passenger side door glass that my friend shot compared to my result so nothing more was learned.
I have to say its tough shooting from inside a vehicle Thur glass and now I will always lower my side drivers window when pulling up to a job. Not very scientific of a test but more of a learning experience.
Thanks very much for the replies everyone. From your combined wisdom, I take it that 9mm will probably not deflect significantly through auto glass (although that won't protect against poor shooting).
After reviewing the ATK results a bit more closely, I see that the results are sporadic. Sometimes the 9mm rounds penetrate far beyond 12 inches through glass; other times they don't make it past 7-8. It seems that the problem is the wide standard deviation. Some of the 9mm rounds you fire through glass might do fine, but others might significantly underpenetrate. This might explain why DocGKR's (presumably averaged) numbers look so good. The larger rounds, on the other hand, seem to penetrate more consistently. Please correct me if I'm wrong.
In any case, I don't think that this is a good enough reason for me to stop carrying a compact 9mm. In the unlikely situation that I had to shoot an attacker through auto glass, a quality 9mm would probably do a good enough job most of the time from most angles. Police officers who make a lot of high risk traffic stops might feel differently. Life is full of compromises, and I'd rather accept this one in a concealed carry weapon than have to put up with the shootability issues of a compact .40 or the bulk of a .45 with decent capacity.
Phila PD,
very interesting...
...an odd question...is there anyone who tested the bullets penetration and behaviour in gel blocks after the glass penetration in the case of the simply and ubiquitous 22 LR 40 LRN bullets fired through laminated glass (..car's windshield..) and car's side windows (..tempered glass..)?
...my question only because in my country some time ago there was a (..serial..) murderer who killed the victims using a 22LR pistol loaded with plated or plain lead RN ammo...the victims were sitting inside their cars...the bad guy normally approached the parked cars from the driver's side to hit the two victims sitting inside shooting through the driver's side window... in one instance it happened that a victim tried to escape after being injuried and it seems that such bad guy was able to hit with a signle bullet the driver's head shooting some yards in front of a car through the windshield...
...I guess that hitting the glass such bullets were at least markedly deformed...and I guess that for such bullet it's a really difficult task to penetrate completely a laminated car's windshield mantaining its integrity...
...some time ago I performed a "poor man's" test to see the pellet deformation and the possibility to have microcristals from the penetrated glass on the pellet using a friend's SEM..."poor man" because I use for semplicity an air pistol...a .177" diabolo pellet....an old pirex lab glass(...about 5/64" thick...)...impact velocity about 450 fps...two pieces of transparent tape on the inside and outside of the impact zone as trick to avoid the glass collapse on impact...
http://img196.imageshack.us/img196/6828/pirex2.jpg
L to R: unfired pellet, pellet after the glass penetration recovered in a paraffin block used as a "soft" backstop, pellet after the impact on the same paraffin block without prior glass penetration.(..the animal gel blocks were in the freezer and they were not available at the time..)
http://img515.imageshack.us/img515/8371/pirex4.jpg
the scale is graduated in millimeters...pellets from above...bottom unfired...
http://img249.imageshack.us/img249/9615/3rdpic.jpg
http://img142.imageshack.us/img142/6052/4thpic.jpg
...images from SEM of two glass microcristals on the bullet's deformed nose surface...
All the best
Andrea
Keep in mind side windows are a whole lot different than double or triple laminated front windshields...
For glass to be a real issue normally requires you to be IN FRONT OF the car as the windshield is much tougher than the side window glass.
Get out from in front of the car.
We have had several shootings with 9mm duty rounds where the bullets gave very good penetration after defeating side or rear window glass.
I'm not too worried about it.
As far as shooting from the inside out; I have found in testing by shooting through Crown Vic windshields that everything fired from a handgun deflects markedly (well, at least in 9mm, .40, .45 and .357mag).
Wayne Dobbs
08-20-09, 08:51
What is going to make things really interesting is when ALL the glass in new cars has laminated glass 360 degrees. I believe this is supposed to start in the 2011 or 2012 model year. Some of the Mercedes Benz and BMW are already equipped this way.
At that point, ammo selection issues with regard to laminated glass performance will get very interesting.
From the OISs I have seen here, I'm still not worried.
Ya never know... the local PD has been consistently lucky through barriers w the 9 for >20 yrs. for example, in the last 10 yrs:
Local PD stopped a bad guy in his car w multiple hits of FBI dissed 115/9 that hit the door, side and front glass before they hit him.
Local SD failed to stop a bad guy w multiple hits of FBI approved 165/40 that hit the door, side and front glass before they hit him. He was hit 7 times (2 face, 2 hands, 3 torso); he jumped from the car, and they had to chase him down.
>12 is better, but <12 is not worthless.
I have a quick question.
Why does Doc not list any 115gr JHP loads in his list?
298436--Look again, there is a 115 gr load listed, the Barnes 115 gr XPB. When another 115 gr load penetrates 12-18" with good expansion in both bare gel and 4 layers of denim, as well as exhibiting adequate performance after auto windshields, it will also be listed...
what do subsequent shots do through auto glass? I'm sure there's a huge difference in performance between shots fired in a string, from outside and inside...?
first shot busts up the glass pretty bad, killing it's deflection ability if nothing else.. fragmenting the glass within the lamination is sure to allow for much better performance from subsequent shots, also.. i'm sure it still effects penetration and round shape to smash through smashed glass, but not nearly so... all correct?
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