How effective would a trained military sniper team be on top of a skyscraper?

Factual Questions
1

Let’s say there’s some event that requires multiple police or military sharpshooters to have a 360 degree field of view on a city. They decide to go to the highest building with a clear line of sight and take up positions there on the observation deck. (For example, I was thinking of the Freedom Tower in New York City, the Willis Tower in Chicago and the Tokyo Skytree in Tokyo) Assuming it’s not a cloudy/foggy day and they have unimpeded views of the ground I have a few questions.

  1. Would a rifle bullet still impart enough velocity to be effective at that height towards a ground target?

  2. With the help of a spotter, could you effectively engage targets at ground level?

  3. Is return fire from the ground possible? Assuming either somebody with a mounted machine gun firing back or somebody with a scoped rifle themselves.

2

The towers you mention have heights somewhere around 1700 feet or so. Assuming that the sniper is shooting down at an angle of 45 degrees, that works out to a distance of a bit over 800 yards.

The way militaries work is that you have infantry grunts who are expected to fight at typical distances closer than 150 to 200 yards or so. Mixed in with the infantry is what is called the designated marksman, who is expected to shoot quickly at targets out to about 600 yards or so. This isn’t a sniper, but they often shoot with “sniper” rifles.

Snipers work beyond 600 yards. They typically work in teams, and unlike the designated marksman, they are shooting for accuracy, not speed. They also work in pairs, and are not embedded with infantry or other troops. Snipers receive more training than marksmen.

800 yards is easily within range of a modern sniper. It’s really not that far outside of the range of a designated marksman, so even a designated marksman could probably be fairly effective at that range.

1. Would a rifle bullet still impart enough velocity to be effective at that height towards a ground target?

Oh yeah. Easily. Not only is the velocity still quite deadly, but the bullet is still extremely accurate at that range.

2. With the help of a spotter, could you effectively engage targets at ground level

Yep. No problem.

3. Is return fire from the ground possible? Assuming either somebody with a mounted machine gun firing back or somebody with a scoped rifle themselves.

Return fire is definitely possible. A modern hunting rifle shoots about 1 minute of arc (MOA), which translates to about a 1 inch group at 100 yards and a 10 inch group at 1,000 yards. Shooting up at someone who is 800 yards away isn’t going to be the easiest shot, but it’s definitely doable.

A mounted machine gun should be expected to be able to put rounds on target out to about 1500 yards or so, and can shoot suppressing fire (not necessarily accurate, but accurate enough to make the sniper on the roof want to duck out of the way) out to several thousand yards. A machine gun will stop the sniper in a real hurry. Depending on the mount, you might be better with a hand-carried machine gun with a bipod. Otherwise, depending on how the gun is mounted, being able to tilt the gun up at the angle required might be a bit of a challenge.

Even a light, hand-carried machine gun is expected to be able to effectively hit a target out to 500 to 700 yards or so, and can shoot suppressing fire out to 2,000 yards or more. You might run through a lot of ammo to get him, but your sniper is definitely within range.

3

Unless they are shooting into a floor or the roof of a nearby smaller building, not much.
The angle is pretty off.

4

Somewhat agree on this. Due to slant range and the Rifleman’s Rule, the steep angle will make this a trickier shot than hitting a target at the same range when the bullet is fired nearly horizontally. I’m nit saying it’s insurmountable. You can guestimate the effect it will have on bullet drop. There are calculators to solve for this factor and experience greatly improves the sniper’s odds. It’s still going to be a tough to to make accurately.

5

Until someone realizes that there is a sniper and where they’re shooting from, taking shots without being detected is no small part of sniper training, the real question is how many rounds are they carrying.

CMC fnord!

6

Two issues I thought of: First, the height difference will add some velocity to the sniper’s bullets, and remove velocity from the bullets of anyone returning fire. But that turns out not to be very significant: A muzzle velocity of 400 m/s would correspond to a maximum height of 8 km, an order of magnitude greater than the heights of skyscrapers.

Second issue, though: If the snipers are on the observation deck, they’re inside, and those windows are very sturdy. I’m sure that a sniper bullet could still go through easily, but I imagine that doing so would totally trash your accuracy.

7

Being that high up you’re dealing with higher wind currents that have to be accounted for. Add to that you’re on top of a building that’s disrupting those currents and surrounding the building with all kinds of erratic turbulence. Making trajectory calculations with variables that are not constant makes for some wide margins of error.

8

Also to add, being that high up they may be firing through layers of temperature changes. Warmer closer to the ground. And those temps are constantly changing also. More dynamic variables, more margin of error.

9

As others have pointed out, a number of factors lead to lesser accuracy. Most can be dialed in with repeated shots except for the gusty wind. I just wanted to point out that shooting either uphill or downhill results in the bullet striking higher then the level aim point** A good hunter should know this, and a good sniper may actually train for it.

The Texas Tower sniper had no problem although that is only about 300 feet high.

** either way gravity has less effect on the bullet then in level flight.

Dennis

10

If I had a red dot suddenly appear on my coffee cup as I was loitering near the street-level entrance to a building, just before it exploded in my hand, would I even be able to hear the noise of the sniper rifle being fired at that distance (800 m) or localise where it came from?

11

A red dot would be useless at those kinds of ranges. I would expect maybe 1 MOA accuracy. MOA is Minute Of Angle, or Minute Of Arc, and 1 MOA happens to be very close to shooting a 1 inch group at 100 yards. So the way this works, that’s having your shots fall into a 1 inch circle at 100 yards, 2 inch circle at 200 yards, 3 inch circle at 300 yards, etc. By the time you get out to 800 yards, your rifle is accurate to within roughly an 8 inch circle. You could probably shoot someone in the head, and center of mass on a human body wouldn’t be too difficult, but you aren’t going to be hitting a coffee cup.

You also have to factor in the bullet drop. Bullets don’t fly in a straight line, they follow a parabolic arc. Snipers have charts and tables for these sorts of things. I’ve never seen one of these charts up close, but I very much doubt that the charts have entries for such steep angles as what we are talking about here. So figuring out the bullet drop is going to be a bit of a challenge. I would expect the first shot to be way above or way below where the sniper wanted it to hit. But once you’ve fired at least one shot, you can get a rough idea for where you have to hold your aiming point. I’m guessing your sniper would need a couple of shots to figure out the proper aim point. After that, they’d be fairly accurate.

Disclaimer - I tend to shoot at paper targets on a level range. I’ve never actually tried to shoot at anything anywhere near this extreme of an angle.

As for the noise, modern rifle bullets are supersonic. The bullet would be through the cup (or more likely, missed it by several inches and went past it) before the sound reached your ears.

In fact, the maximum accurate range of modern rifles has a lot to do with the speed of the bullet and the speed of sound. The bullet starts out supersonic, so it creates a shock wave in the same way that a plane flying faster than the speed of sound creates a sonic boom. As the bullet slows down due to air resistance, the bullet eventually transitions from supersonic to subsonic. At that point, the shock wave catches the bullet, and the chaotic pressure of the shock wave makes the bullet tumble and veer off a bit in a random direction away from its intended target.

You wouldn’t hear the bullet until it went past you, but you’d probably have a good idea of roughly which direction it came from.

In an urban environment, the sound might echo off of nearby buildings, which might make the sound’s origin difficult to locate.

12

High Rises have a natural up draft. So depending on how many and how close other high rises the winds could vary through out the distances. And there would also be temperature differences.

13

The whole “red dot = sniper” trope is more to do with movies than real life. In real life, snipers use optics. If you are already looking through a scope or electro-optical sight at someone, you have the means to shoot them with that alone. You don’t need a red dot. All the red dot does in such a situation is tip off the target (or, in reality, the audience) that a sniper shot is coming. It’s a terrible idea.

What red dot sights are used for in real life is more close range, even point blank shooting when there isn’t enough time to take aim through a sight. Things like SWAT clearing a room. You see the target, you put the dot on the target, and you shoot the target. Hopefully before they shoot or otherwise assault you. It’s already taken as a given that they know you’re there and have a gun on them, so the red dot isn’t giving anything away.

14

not quite what the OP meant but Charles Whitman did a job from 28 stories up the UT tower in 1965

15

If I may go slightly OT… Charles Whitman was not a sniper. He, like Oswald, was a murderer who knew how to shoot a rifle well enough for the marines, which is… merely okay. Anyone with a modicum of training can shoot people going about their daily lives, walking in a straight line like nothing is up, or just covering behind a bush, praying for the carnage to end. It’s really not that hard to kill a lot of people, if all you mean to do is kill a lot of people. You just have to be the scum of the earth (or perhaps, more charitably, deranged) to actually go and do it.

He was not a sniper, he was a murderer. With a growth on his brain that may or may not have affected his judgment (it’s debatable).

So, I guess, yeah, a trained sniper ought to have no problem. Apart from the moral quandaries related to who they’re shooting at. I mean, if a couple of unexceptional men like Oswald and Whitman could do it…

16

The OP is talking about 100+ story buildings. A sniper wouldn’t be able to shoot someone at the base of the building just due to the angle; any victim would need to be out a ways.

I doubt one could even hear/recognize much less locate a single shot from that distance in an urban environment (¼ mile vertical + x blocks horizontal mixed into the cacophony of traffic & people). The first shot could be random to take out the window; how many skyscrapers have laminate glass (like car windshields) where the sniper would need a number of shots to do anything other than make a small hole?

According to Wikipedia, the Las Vegas shooter used a hammer to break out his windows, but they were only on the 32[sup]nd[/sup] floor.

17

A friend of my neighbour stops by for a day or two each time he passes through. The first time I met him, he was unloading his pickup, including a gun bag. I asked him what he was hunting, but he avoided answering. Once he got to know me better over the years, it was fascinating to learn about what his job entailed.

There are people who do precisely what you are wondering about who are part of the security provided when there are major conferences of world leaders.

18

Skip shooting through glass. Go instead to a machinery/HVAC level, which are often on top of the building, screened from view by metal louvers or a small parapet. Make a hole in either for your observation and firing position.

Good ballistics calculators will include sight angles. Play around with something like JBM Ballistics free online calculator, and you’ll see that sight angle will make a gigantic difference in the amount of drop you have to account for.

Police marksmen, like who famously are at things like NFL games, not only have to account for sight angle when estimating the path of their bullets, the point of aim on the target changes. With a high enough angle, a point of aim on the front of the target’s head, between the eyes for example, may result in the bullet not intersecting the area of the brain necessary to stop the target’s dangerous activity.

Wind dope will be challenging in the OPs scenario, as it will be large and variable.

19

If you want to argue that Oswald doesn’t deserve to be called a sniper because he didn’t go to sniper school, or because murder is bad, that’s your own quest. But Marines are very well-trained with rifles to a level that exceeds any objective definition of “okay”, and that’s what enabled Whitman to harm so many people.

20

Oswald positioned himself inside a hundred yards from his target, traveling away from him in a nearly straight line, and with minimal angular velocity relative to his position. This really was not that skilled of a test. He was a marine, and marines pride themselves on marksmanship, yes, but it is nowhere near sniper levels of training and, as a marine, Oswald was a mediocre shot (the sharpshooter rating which he initially achieved, contrary to its name, is actually the middle of the three passing ratings, and he later was downgraded to marksman, the lowest of the three).

He was not, and did not have to be, an exceptional shot to shoot Kennedy in the back of the head. He just had to lack the sort of inhibitions that (I hope) you and I possess that would keep us from attempting something so terrible, and so incredibly pointless.

Of note, the longest range kill by a sniper is about 3.5 kilometers. While I am sure shooting from a greatly elevated position and at an extreme downward angle would complicate the calculus going into each shot, I’ve got to believe it’s at least possible for a trained military sniper to score hits from the top of a skyscraper. What I question, though, is if a properly trained sniper would even choose to be in such a position.

Skyscrapers are large enough, and tend to have enough auxiliary and communications equipment on their roofs, that a single sniper team would likely never get a full 360-degrees of coverage. Is the question in the OP about trying to achieve realism for short story, or is it just asking out of curiosity?

ETA: I apologize for the intermittent threadjack, but I hate to see men like Oswald and Whitman trumpeted as being exceptional in any way, when they weren’t. Except as criminals, and only in as much as even most criminals probably would shy away from doing something so heinous as what they did.