Advanced Marksmanship Shooting from a moving plattform! Maritime sniping.

hastoltz

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Feb 1, 2014
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The following ballistic calculation challenge was identified during a realtime ops as a maritime sniper:
Im european so sorry for the metric values, but the principle is the same, only the units is different...

The following scenario takes place: you are a maritime sniper providing security on a vessel protection detachment. you have set position onboard and a suspicious contact appears.

There is a threat onboard a small static wessel on your port side 800m away.

Your own wessel is cruising stedy at 20knots(~10m/s)
Your weapon is a barret M81A2 50cal.
True wind is 0m/s
Flighttime to target is 1,18s
Reactiontime is 0,25s
(Other enviromental frictions not estimated)


Point of aim --> + [target] <----(static).
Distance 800m

^ (bullet)


SOG:20knots ~~~ [::::sniper|:::::>. (Moving at 10m/s)--->


Sog: speed over ground


WHAT ARE YOUR LEADS?
In order to hit your target you must hold a lead behind the target in order to compensate for drag caused by lateral drift(speed of your own wessl/moving plattform) ant wind effect on the bullet.



It is a fact that a lateral drag is generated on the bullet because the movement of the plattform it is fired from. And that this sideways velocity would be decelerated by the air. The bullets ballistic coefficient must be a factor in determening deceleration rate, and airpressure / density alt.(DA)

Around the wessel a headwind is generated, the headwind in this example is 10m/s (20knots/2=10m/s)
This headwind is affecting the trajectory of the bullet in the first part of its flight, and is also decreasing the lateral drift.

A number of factors are changing throughout the trajectory of the bullet, and a correct firing solution is hard to calculate, however it is possible.

* What needs to be determined is if the lateral drift is equalized by the headwind?
*How much reactiontime and triggertime has to play in determine your leads?
*How many percentages of the flightpath does the headwind play a factor and how much have it decelerated lateral drift in total?

What i do know, and have tested is using a chart for moving target, and it can not be reversed to get a fireingsolution. In reality the leads (holds)was to much and the hits was far beyond the target....

I know one ballistic calculator that has the option of choosing speed of the platform you are shooting from (aerial engagements/helos) the AIM-E, but short of it i need a formula to generate a table for a Lead chart to my unit.i also want to understand the theory behind the formula.

Im currently downrange so i reach out to snipershide and to all the bright minds for help..



Best of luck! LT.Stoltz
 

kraigWY

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I use to hunt seal (furry ones) with the Alaska Natives when I was the CO of an Alaska Native Guard Unit. The biggest problem is no the lateral movement of the boat or the target. The biggest problem is the boat and target are bobbing.

You can figure it out after a while but I don't know any formula for it.

There is a more practicable way to practice I suppose. Every time we visit my MIL, she wants me to kill turtles in her ponds. Turtles only expose their little bitty heads, which is bobbing in the water. I only shot them from the bank, but if one wants practice, paddle around in a canoe on a windy day, shooting turtles.

Some things you just cant practice with a formula. Just takes a lot of bullets down range,...............or over water.
 
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KYpatriot

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The movement of the boat imparts an initial velocity to the bullet in the direction of the boat's travel. Then you could use trig and the TOF of the bullet to determine how much "drift" this component would cause during the TOF. If the boat is not getting closer or farther from the target then this drift would be a simple horizontal component requiring "negative lead" to counter.

While the bullet is in flight this will create a crosswind and I would think you would have to subtract the drift due to this "crosswind" effect from the drift calculated for the boats movement. You would also have to account for any actual wind in the appropriate direction as normal.

It would be very difficult to calculate all that on the fly, not to mention bobbing up and down randomly on the water. This is why belt feds and tracer were invented !
 

MAGUA

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First thing i would do is disable the " wessel " so it remains static and then decide what action to take next against the threat on the "wessel".
 

mallrat

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Aug 8, 2013
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I use to hunt seal (furry ones) with the Alaska Natives when I was the CO of an Alaska Native Guard Unit. The biggest problem is no the lateral movement of the boat or the target. The biggest problem is the boat and target are bobbing.

You can figure it out after a while but I don't know any formula for it.

There is a more practicable way to practice I suppose. Every time we visit my MIL, she wants me to kill turtles in her ponds. Turtles only expose their little bitty heads, which is bobbing in the water. I only shot them from the bank, but if one wants practice, paddle around in a canoe on a windy day, shooting turtles.

Some things you just cant practice with a formula. Just takes a lot of bullets down range,...............or over water.

A while back I saw a video with a shooter firing from a platform suspended on automotive springs to provide an unstable base. Could set it back from the pond's bank to increase the range. Or simply shoot from the back of a pickup (check local laws).
 

Gunfighter14e2

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If your on a vessel large enough to have a team aboard, you should have access to equipment that is/was designed for that task.
(Gun an ammo are the cheapest component)
 
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Johan L.

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Jan 19, 2014
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If you exclude the wind caused by your moving platform then you can calculate the lead by using the formula for a moving target and stationary gun. To that you would have to add the effect of the virtual wind caused by the moving platform. The movement of the platform will require less lead no question about that. Applying a 10 m/s crosswind will over estimate the effect as the virtual crosswind will decrease along the fligt path. Question is how fast?

One good estimate could be to look at the drift of the bullet caused by a constant 10m/s crosswind at the actual distance and assess what lateral speed the bullet will gain after that specific flight time. It must be a good guesstimate that the original lateral velocity of the bullet will decrease with the same amount at that distance.


Looking at one of my 308 loads using my ballistics app in my Iphone I see that a 10m/s crosswind deflects the bullet 4.1967 meters att 800 meters using all decimals. Flight time to 800 is 1.39 seconds. That means that the mean lateral velocity has been 4.1967/1.39=3 m/s during the bullets flight.

With this defined I believe I would get close if a calculate the lead for a moving target with 10 m/s at 800 meters minus the wind deflection at 800 meters caused by a 7 m/s crosswind.

With my 308: flight time 1.39 sec, target speed 10 m/s gives a lead of 13.9 meters. Wind drift from 7m/s att 800 meters =2.9 meters. Total lead would be 11 meters when the bullet exits the muzzle.
 

fdkay

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    personally, since, the target is static, I would have the OOD reduce speed to the point that they just maintain steerage way.
     

    BGE541

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    D/VxS=FV Lead in Feet... Go from their. Works for leads both ways. Did they train you guys for this or what? Kinda a big step here in shooting (ability/capability) to just "hand" the answer too (not like the information makes it easy) Just sayin'
     

    Papa Zero Three

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    Lt. Stolz,
    Yes, lead charts can be generated for the scenario you presented but the only easy way I am aware of is by using AIM-E as it takes into account all the variables you mentioned to include your zero range, your bullet information, angle, temperature,spin drift,etc. The info charts produced do not take into account user reaction times, trigger manipulation, obviously.

    There are 4 scenarios you will likely encounter:

    1. You and the tgt are moving parallel and at the same speed
    2. you are stationary and tgt is moving
    3. you are moving and tgt is stationary
    4. you and tgt moving at different speeds and or directions

    In your case above, you will have to compensate for your movement and for the drag created by that movement. The formula to use is:

    time of flight x target speed= INVERTED LEAD

    This will give you a value of how much BEHIND the tgt you have to aim. Conversely, this same formula can be used for scenario #2 above to determine your lead in front of the tgt. Look at the drag/headwind as a straight side wind. Look at your data book for wind value/distance and then add the 2 values (speed and drag) for the right lead.

    Speak with the helm for determining your speed and tgt vessel speed; have a GPS with you so you always know your speed. If the relative wind is obtained from onboard/helm instruments and used in your solution,you only have to compensate for speed as the drag is included in the relative wind value.

    The best way to develop this info is to actually do it and record what solutions work for you. This is time and ammo intensive and not always possible on a boat. And again, any chart you develop is a guideline/starting point at best. The only thing I have personally used and found to be quick and accurate for any of the 4 above scenarios is the solutions AIM-E's moving platform feature produces when you fill in the required info and let it calculate it for you. As a side note, it also works when shooting from flying platforms (helos).

    *Note: This is in no way everything that needs to be taken into account when shooting from a vessel and I intentionally didn't cover other considerations simpley for brevity and to answer the OPs question.
     
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