Hey DU Shooters! I've Got A Question

[ProfessorGAC]

A young girl was killed here in Chicago last week. (An even younger one was killed over the weekend in the same neighborhood, but that's for a different topic.)

This 14 year old honor student is standing in the window of a 2nd floor apartment when an assault rifle bullet rips through the glass and kills her.

Now it turns out that the guy who did the shooting was firing at someone else, but was over 2 blocks from the house the girl lived in.

Now, i don't have a rifle, never did and have never fired anything other than a handgun. However, it occurs to me that the guy who shot this girl had to be a HORRIBLE shot to have missed someone by so much that the bullet was still 12 or 15 feet in the air at a distance of two blocks. Am i wrong about that? I just can't figure out how one could be shooting at one thing and still hit something else, that high up & that far away.

So, it would appear that gang members having guns isn't just a bad thing because of bad intentions, but if i'm correct, it's a bad thing because they have no idea as to how to use one.
The Professor

[Spider Jerusalem]

1. Christ, that's terrible.

And the shooter would've had to be a VERY bad shot, or a total moron who had no familiarity with the weapon he was using (not that gang members who are PROFICIENT with assault rifles is a good thing, either).

Let's say two blocks is roughly 400 yards...so roughly double what's considered effective range for an assault rifle (when aiming at a target on a level trajectory)...he'd have to have been aiming a few feet high, at least, I'd say; and if the weapon was fully automatic it could be that he was too much of an idiot to know to fire in bursts--the recoil from sustained full-auto fire causes the barrel to climb and move to the right (assuming a right-handed shooter).

[ret5hd]

2. A few years ago i was watching a documentary...

about the gangs in little rock arkansas. "Gangs in little rock?", i thought. "How bad can it be?"

well, it turned out that one reason it was so bad was that the gang members there (being from a relatively rural area) were REALLY good shots, and practiced all the time. When they wanted to shoot you...they did.

[xultar]

3. There was a case like this on CSI...if the shooter was trying to shoot

UP to get the guy it is very possible that it would have been coming down on the arc when it killed the girl.

That is why in NOLA on New Years they beg people not to shoot guns in the air because what goes up must come down. Some people had been hurt and/or killed by falling bullets from miles away.

[Blue_Tires]

5. i saw that episode too

i was going to mention it

[Richard Steele]

4. You have a link?

Hard to offer any opinion with such vague info.:shrug:

[ProfessorGAC]

6. Chicago Tribune

I read it yesterday in the print edition. Should be online too, i would think.
The Professor

[Richard Steele]

9. Thanks.

Edit: your question about the gunman's "accuracy"
seems sort of unanswerable, as the story makes it clear
he was just spraying bullets wildly across the neigborhood:

"That person was not hit,
but the gunman sprayed 29 high-caliber rounds
up and down the street, hitting at least eight houses,..."

This was not "bad aim", this was absolutely NO AIM AT ALL.

[johnnie]

7. I wouldn't say "bad shot"

More like a Cheney shot.

I think a lot of the punks out there shooting each other up watch too much TV and think they are playing cops and robbers. They probably don't care if they "accidentally" shoot someone else either. A slug from a firearm can travel quite a distance before it drops to earth. Usually something will stop it before that point.

Here is some pretty good information for ya to read:

http://www-medlib.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNBLST.html

[mcscajun]

8. His trajectory wasn't level from the beginning.

He was firing from a car window Up towards a porch (the articles don't specify how high the porch was, though).

Twenty-nine rounds let loose? Sounds like he was just spraying the gun back and forth like some old movie gangster.

[ProfessorGAC]

10. Well That Explains It, I Suppose

But, still to hit something even higher than one is aiming at that more than twice the distance would seem to be an indicator that the shooter didn't know what he was doing. Just seems like a really bad shot, to me, but like i said, i don't know.
The Professor

[benEzra]

11. 15 feet at 400 yards is an aiming error of 0.7 degree...

way off for a skilled shooter, but believable for an idiot shooting from a car.

No one actually knows what kind of gun was used--could be a Ruger Mini Thirty (low-powered deer rifle) and aftermarket magazine, an SKS with an illegal mag, a civilian AK lookalike, or a real (and highly illegal) AK-47 smuggled in from South America, for all we know. Police reports indicate the caliber was 7.62x39mm, though, and ballistically all the foregoing are the same. So we can just look at the caliber and make some guesses. (BTW, the reporter was wrong about the "high caliber rifle" part; 7.62x39mm is the least powerful of all .30 caliber rifle rounds, only about half as powerful as a .30-06.)

I ran this through an online trajectory calculator (http://www.eskimo.com/~jbm/ballistics/traj/traj.html), assuming the caliber was 7.62x39mm. Data for the calculator: Ballistic coefficient is about 0.33, bullet weight is 123 grains, bullet diameter is 0.311", muzzle velocity is 2350 ft/sec (slow for a rifle). Sight height is around 2 inches.

The calculator spits out the following:

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yds) (in) (moa) (in) (moa) (ft/s) (none) (ft-lbs) (s) (in) (moa)
0 -2.0 *** 0.0 *** 2350.0 2.105 1508.0 0.000 0.0 ***
100 -0.0 -0.0 1.3 1.2 2099.4 1.880 1203.6 0.135 23.8 22.7
200 -5.9 -2.8 5.5 2.6 1865.0 1.670 949.8 0.287 50.5 24.1
300 -21.9 -7.0 13.2 4.2 1648.8 1.477 742.3 0.458 80.6 25.6
400 -50.7 -12.1 24.8 5.9 1454.6 1.303 577.7 0.652 114.7 27.4


So at 400 yards, a round would be 50 inches below point of aim IF the shooter knew enough to use the close-range 100 meter sight setting (the default sight setting on most imported 7.62x39mm rifles is 300 meters, and I don't know if your average criminal would know that). Add 50 inches to the 15-foot elevation of the victim, and you're looking at about 1 degree of aiming error.

I'd have to chalk this up to the idiot shooter. Criminals aren't exactly known for their marksmanship; most have never owned a legal firearm, have never been to a rifle range, have never had any marksmanship instruction, and know next to nothing about guns, gun safety, and ballistics.

[ProfessorGAC]

12. Thanks.

I figured out the ballistics, but i didn't know how much error was huge or how much was typical.

I would think that a rifle with 0.7 degrees of error would be useless for wartime. So, you're likely correct. The shooter is a boob.
The Professor

[benEzra]

13. Yep. And also a monster...

FWIW, I own a civilian AK lookalike (Romanian SAR-1), and it's capable of about 2.5-arcminute groups on a good day, and 5 arcminute arcminute groups on a bad day with crappy ammunition and a hot barrel. Other 7.62x39mm rifles are comparable. That's only 10 to 20 inches of inherent dispersion at 400 yards.

A good bolt-action rifle with premium ammunition and good optics can often shoot into 0.5 arcminutes or better from a cold barrel, from sandbags or a bipod, but most rifles will fall into the 1 to 3 arcminute range.

[northzax]

14. not military standard

but not that far off, in reality. It's not that easy to shoot a weapon accurately, especially with adrenaline pumping and the recoil. a couple of weeks ago, at a club near my house, a guy shot, across a two lane road, 21 rounds at three people and managed to hit one of them, in the leg.

Last week, in a truely freakish incident, a man was killed leaving a bar at 3 am, shot, with a pistol, from two blocks away, completely random. THe shooter missed his target, and hit this guy in the head, killed him instantly.

[ProfessorGAC]

15. Well, We Have A Difference Of Opinion

Some say a decent shooter couldn't miss by that much, others say opposite. I guess i won't be able to understand it either way, since you guys know so much about this stuff and i know nothing about it.
The Professor

[northzax]

18. this is the problem with high powered firearms

your aim doesn't need to be off by degrees, only minutes or seconds to miss your target and hit something else. And few people can actually shoot accurately, under pressure. look at all the times that police, who are actually trained somewhat, to shoot, throw 90 rounds at someone and hit them twice. an untrained person isn't likely to hit a target from more than 5-7 feet, with a pistol.

[ProfessorGAC]

19. Makes Sense To Me

But i guess i could see missing left or right. Even by a lot. But, missing up is the part that made little sense, unless someone was completely incompetent.
The Professor

[northzax]

20. the recoil goes up, right?

I haven't shot a weapon in a long time, but I think missung upwards is common from the recoil, especially for someone who isn't trained to use the gun (or firing from a non-secure stance) so second shots often go high.

[ProfessorGAC]

21. I Guess So

Like i said, i don't anything about guns.
The Professor

[Greyhound]

22. It is a military round used by half, or more, of the militaries on earth.

It's not as common in the US military, which uses the .223, much smaller higher velocity round.

[northzax]

23. I meant the shooting

not the equipment. :)

[Greyhound]

25. My bad, apologies. n/t

[Squatch]

16. Doesn't Chicago have a ban on assault weapons?

"Chicago (§ 8-20-030(i) and 8-24-025) bans the transfer, acquisition or possession of assault ammunition (any ammunition magazine having a capacity of more than 12 rounds)."

[ProfessorGAC]

17. Well, That Didn't Work

I don't believe in blanket prohibitions anyway. I don't think they've ever worked on anything.
The Professor

[thirdpower]

24. It's illegal for citizens...

Not King Dick and his entourage.

In retaliation for the shooting, he's demanded that all firearm owners in Ill. come to his office and justify why they shouldn't have all their firearms banned and confiscated.

[rfkrfk]

26. what gun/round was used?

at 400 yards, an assault rifle is a poor choice

better would be ordinary hunting rifle

[benEzra]

27. Police think the caliber was 7.62x39mm...

no idea what kind of gun was used. The most common rifle in that caliber is the SKS (most popular rifle in America, IIRC), followed by civilian AK lookalikes and the Ruger Mini Thirty.

The 400 yard shot appears to have been an accident; I think the criminal was shooting at someone close by and a stray round hit the girl two blocks away.

[NNN0LHI]

28. Ricochet is a distinct possibility

Just hitting a small tree branch can alter the bullets trajectory.

Don