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Assuming that you are flying in a powerarmor with the help of magic to assassinate/kill flying sorcerers/Forward Observers/officers.

The rifle that will be used in this question will be McMillan Tac 50 shooting a modified .50 BMG bullet that has 90% reduction to air resistance and bullet speed has been modified to 1500m/s. Recoil has increased by 130%(I dont know how hard the recoil will be with the increase speed of the bullet(since faster bullet means probably more gunpowder used and thus has more recoil)

Maximum altitude is 24000 feet with the help of oxygen supply from power armor

How will it affect long range accuracy while shooting at this speeds

15km/h

20km/h

30km/h

45km/h

60km/h

120km/h or higher

accurately shooting something at this distances

250m

500m

1000m

2000m

3000m

4000m

5000m~

also how hard is it to shoot something downwards assuming that you are 24000 ft in the air and your enemies are like 18000-22000 ft below you using the same gun and cartridge?

Is it even possible to shoot and kill/heavily damage a person that is flying/riding at speeds of 30-90km/h without the help of tracking computer installed in the scope?

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    $\begingroup$ When you're asking how firing a gun and accurately hitting a target while magically flying and possibly moving at high speeds the best line of thought should be to think about how it actually happens. Think of how planes fire at each other and how difficult it would be to hit a target with a single sniper shot. The best bet is a guidance system or the tried and true spray and pray. I know this doesn't answer your question but it should give you an idea of how difficult it is and why it isn't done in the real world. $\endgroup$ – Virusbomb Oct 24 '16 at 14:50
  • $\begingroup$ @Virusbomb so basically if i hover in prone position and achieve a steady state, i can successfully snipe? $\endgroup$ – mico villena Oct 24 '16 at 14:53
  • $\begingroup$ This...seems more like either a Physics or a Gun dedicated question, which do belong to the respective boards... $\endgroup$ – Trish Oct 24 '16 at 14:59
  • $\begingroup$ Hovering in prone isn't really important since being prone only helps when you're using the ground to steady the aim. If you're already achieving a perfectly steady state then you could be prone, or standing or up-side-down. Given that you're stable and if you had an easy stationary target you still have the issues that current snipers have with wind, temperature, pressure, speed drops, gravity, and everything else I can't think of, plus amplified and more complex with the altitude making it worse. A moving targets is about the same but you have to predict where they're going to be exactly. $\endgroup$ – Virusbomb Oct 24 '16 at 15:15
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    $\begingroup$ Guided projectiles are the way to go. NASA hit a target within 660 feet from a range of over 300 million miles. They called the projectile Spirit. $\endgroup$ – Kys Oct 24 '16 at 18:47
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Vibration is your enemy. The reason it is hard to snipe things is that tiny motions of the weapon can translate into much larger changes at a distant target.

If you assume that your weapon is 1 meter long and that your target is is 1000 meters away, than a 1 millimeter change in the tip of your weapon translates into a 1 meter change on target. That is probably enough to miss an evil wizard. If you are flying in powered armor, there is probably enough vibration from your suit's engine, or from wind resistance of flying through the air, to put your shots off target.

The second problem with sniping at long ranges is the wind. Especially with your proposal of sniping enemies 5000m below you, the sniper has basically no way to telling what the wind is going to be like between here and there. Even with a big reduction in aerodynamic drag, cross-winds will still make a big difference on your longer shots.

Lastly, regarding shooting and killing people flying at 30-90 km/h: In WWII people shot at and killed airplanes with .50 cals. Those moved faster than 90 km/h, so this is definitely possible, although a high rate of fire is probably desired.

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    $\begingroup$ "although a high rate of fire is probably desired" <- quantity has a quality all its own. $\endgroup$ – AndreiROM Oct 24 '16 at 16:03
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    $\begingroup$ The M2 was the best sniper rifle in the world for 35 years, out of the 95 that it's been in production. And unless your name is Rob Furlong or Craig Harrison, it still is. "Snipers firing from trees were engaged by the quad gunner at trunk level - the weapon would cut down and destroy the entire tree, and the sniper with it." $\endgroup$ – Mazura Oct 25 '16 at 5:17
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You have made a few assumptions here. For starters, higher bullet velocity doesn't necessarily mean increased recoil. If the bullet WEIGHT has been reduced, the velocity can be higher with no increase in recoil. Of course pressure goes up if you just increase the amount of powder in the cartridge (or use a faster burning powder). However, 1500 m/s is VERY FAST for a bullet. For example, a good match bullet for the .50 BMG, the Hornady A-max, has a muzzle velocity of 2820 fps with a 750 grain bullet for 13K foot/pounds of energy. By comparison, your 1500 m/s (4900 f/s) bullet, if it were also 750 grains, would be a whopping 40 THOUSAND foot/pounds of energy, so THREE times the energy! Even reducing the bullet down to a svelte 450 grains would still be 24,000 foot/pounds, almost twice the energy.

Some of the fastest wildcat rounds are in the 4500 f/s range but these are usually very light bullets in a much smaller caliber. For the .50 BMG those velocities are more likely in a sabot round which would also be very light, as trying to push a heavy bullet that fast would require some very high pressures and a very tough bullet. But we can just handwave the mechanics of the gun. Since this is power armor there is probably some sort of gun stabilization system as well.

Bullet drag (which affects air resistance) is usually a function of the bullet profile, while bullet stability in flight is also affected by bullet spin and weight. In general, heavier bullets maintain their velocity better and are more accurate at longer ranges as they are less likely to deflect due to wind but clever bullet shape can offset this quite a bit.

For your scenario it would be VERY difficult for any human to make these shots without computer targeting. Various altitudes mean different air density, the higher the altitude, the lower the air density, the less drag on the bullet. Firing up or down is a tricky calculation. To have both the shooter and the target in motion is also extremely challenging. There are "smart scopes" that can sample atmospheric data (wind speed, air density, temperature) and incorporate a laser rangefinder in order to adjust the point of aim to increase the chance of a hit. But even then, firing single shots of non-guided projectiles will be of little use if the target is moving in an unpredictable way. There is a reason why almost all air defense systems use a high rate of fire to saturate the area, altitude timed exploding rounds (flak), or guided missiles.

The .50 BMG maximum engagement range for a precision shot is around 3100 meters. That is an EXTREME range for hitting a person (and is long range even hitting a plane or vehicle). So some of your engagement ranges are very optimistic. Firing from a high position all the way to the ground is also difficult. The bullet still has to travel 24,000 feet through air (assuming you are shooting straight down, not at an angle), so while it is getting assisted by gravity it eventually drops to terminal velocity, begins to tumble, and accuracy suffers. The extreme velocity of your gun would mitigate a lot of this, assuming it had a damned good bullet to take advantage of all that speed, but it is still very difficult to make precision shots 3 miles out.

What your armored flying snipers probably want is something like the Barrett 25mm XM109 anti-materiel rifle, shooting mini grenades. It is similar to the XM25 concept they wanted to field for the US Army. Fire the grenade and it is timed to explode at a specific range. You need a certain caliber in order to have an effective grenade, currently that is a minimum of 25mm or so, twice the diameter of the .50. Obviously if you had magic or advanced tech you could make the grenade smaller and fit it into the .50 round. The advantage of grenades over conventional bullets is that you don't have to hit, just get close. This is much more effective for the speeds and ranges you are looking for. Of course if the target is armored then an exploding round may not penetrate and you are back to needing a direct hit, but you don't elaborate. But the 25mm rounds could have a contact detonation option and would still be a better long range option since larger, heavier bullets tend to be more accurate at extreme range (assuming you fire it fast enough).

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  • $\begingroup$ I like this answer, this gives me alot of idea on my end on how to mitigate inaccuracy of ultra long range shots $\endgroup$ – mico villena Nov 5 '16 at 11:57
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The art of snipping in and of itself is basically black magic. (see Archer's Paradox) So basically, if it's repeatable under identical circumstances, a good sniper can hit it. However, if you have power armor + magic, than you can make it more believable with adding Smart Bullets (in this case, bullets that can self correct to a degree for wind/drag/ect, or if the sniper can focus on the target for a couple seconds, self guiding bullets)

The bullets will loss power over distance, even firing down because air resistance, but that can be overcome with heavy enough bullets or load high explosive/thermite rounds (or high explosive armor piercing thermite rounds, whatever sounds cooler for the story X3)... I'll leave the math of that for someone else.

(I'd recommend looking up explanations of how archers can shoot targets out of the air smaller than the wobble range of the arrows they shoot)

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Precision shooting from an aerial platform at low altitudes (below say a couple hundred meters) is certainly possible -- the USCG uses .50 cal snipers on helicopters to interdict drug-smuggling fast boats.

The main problem is when that platform starts to move -- hitting something when you're on a moving platform isn't much easier than hitting a moving target, and at significant speeds, figuring out where to aim in order to hit the target is quite hard. Hence, aerial gunnery at anything faster than early WWI biplane speeds practically requires rapid fire weapons -- look at how rapidly machine guns were mounted to aircraft in WWI for your guidance here.

Furthermore, if you try to put your shooter way high up -- the winds just become awful as winds at altitude are in no way reflective of surface winds, and can move much faster than the surface winds as well.

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  • $\begingroup$ Snipers rely heavily on signs which tell them how the wind is moving, such as grass and tree movements. The wind can actually change direction part way through a bullet's flight, so you need signs at many places downrange. As you point out, there will be no such signs at altitude. This on its own will be enough to sink the idea of an airborne sniper sniping people at long ranges. $\endgroup$ – Cort Ammon Oct 25 '16 at 15:58
  • $\begingroup$ @CortAmmon: In an aircraft, they have way superior devices for determining wind speed and direction at their disposal. They just need to glance over the pilot's shoulder at the dashboard. In magical flight though... $\endgroup$ – SF. Oct 26 '16 at 16:11
  • $\begingroup$ @SF. Those tools will tell you what your windspeed and direction is at the plane. You need to know what it is a kilometer or more away from the aircraft. $\endgroup$ – Cort Ammon Oct 26 '16 at 16:52
  • $\begingroup$ @CortAmmon -- the problem's equivalent to detecting clear-air turbulence before you hit it $\endgroup$ – Shalvenay Oct 26 '16 at 22:23

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