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brown dog

Inclined Fire - a technical discussion.

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Well, as we're locked down, and I'm a wee bit bored, who fancies some ballistic nerdity fun?!

 

I've just had the fb post below pointed out to me. 

Anyone like to chip in with an assessment of the post's technical veracity?  (Some starter questions below)

[If you can't see the clip, the shooter takes on an 800m target at a down angle of 30 degrees from the prone position. The shooter then rises to a kneeling supported position and re-engages the same tgt]

Screenshot_20200423-190057.thumb.png.08482b4b554f219a54f43fb6c42293b1.png

Screenshot_20200423-190105.thumb.png.fceb94f3221ea4108ee986f752b3826c.png

https://m.facebook.com/story.php?story_fbid=123971809261350&id=110239403967924

 

Starters:

Meaning: "High angle shooting"   -discuss

Concept: "True gravitational distance"  - discuss

The effect at 800m of: 'Increased angle to target on moving from prone to kneeling'  - discuss

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Evening brown dog, 

 

Hope you don't mind me jumping in as that's my FB post, I can attest to the technical veracity of the post. High angle shooting is something taught in sniper schools all around the world (having attended one myself), it's simple Pythagorean theory (I've attached a photo which will maybe explain it better) that everyone gets taught in school. Now i should say that the video is merely an example of someone shooting at a relatively high angle, he wasn't shooting at 30o nor at a target at 800m, and in his case changing from the prone to the full on standing would probably only been a 0.2 MRAD difference, but if he was only hitting the edge of a plate that can make the difference between a hit and a miss.

Regards, 

Jack   

diagram-of-angle-needed-to-hit-target-from-above.thumb.jpg.931734c5e0eaf58591a1c6f060e1d3ae.jpg
 
 
 
 
 

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I've found in the PRL matches that I've shot the angles are never really very 'high' and the distances so short that to just aim at the lower half of the target usually suffices. The theory is right though its just that the practical application, due to the limits of the available shooting spaces in the UK, means that it does not make a great deal of difference on target if the calcs mean the target is +/- 10 Yards/Metres different between horizontal and line of sight distance.

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It's not something I thought about before but the laser measures in a strait line and the bullet has trajectory which is longer than the strait measure of the laser..

I'm not sure if this is calculated into the equation on your ballistic app or not 🤔

 

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Isn’t high angle referring to artillery - mortar fire 

 

Rifle shooting at steep angles would in my view be referred to as incline fire 

From my own understanding and after partnering BD at several military comps in CZ to work out the actual ballistic solution one would actually multiply the solution to slant angle distance  to target distance (eg 800 mtr - 61 mrad by the cosine of the angle 30 degree

 

Therefore 61x 0.866 = 53 

 

Solution to target 5.3 mil 

 

It isn’t a particularly challenging incline - common in deer killing scenarios (angle not the distance )

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Cos x flat range distance as in the post above is known as the riflemans rule, its been proven less accurate than cos x dope (known as improved riflemans rule. This however depends on your rifle being trued correctly ie dope is correct.

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Seen ‘high altitude’ courses ie where both angles and physical elevation ( ie ‘thin air’) are encountered?

.. high angle shooting? Thought that was shooting at an elevation greater than the maximum range of a weapon  ie like a mortar?

But looking at the example of shooting 30 deg downhill prone then standing behind say a 1m barricade and then shooting at the same target, quickly  drawing that out it’s a change of .062deg in LOS or .0005 Difference in cosign value if my math is correct? but open to correction here, always ready to learn 
 

Think there are other things to worry about ongoing from prone to barricades?

just saying?

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Ok so using my applied Ballistics taking the Facebook method aka riflemans rule the app gives me a correction of 7.2 mils at 0 deg of elevation and 5.6 mils at a range of 692 m at 0 degrees of elevation. 

Taking the original elevation of 7.2 mils and multiplying by cos (30) =0.866 gives 6.2 mils of correction 

putting the angle of elevation of 30 degrees into applied Ballistics with 800m range gives a scope correction of 6.1 mils. This is clearly far closer to the improved riflemans rule providing of course Brian Litz has done his sums properly (which I bet he has) 

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Some on the ball answers😊  to those of you who've done well: well done. 

Q1:

High angle fire is an indirect fire term, meaning fire in the upper register or, as some have said, fire at elevations higher than that at which max range is achieved.  What we're talking about here is inclined fire.

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Q2:

Equivalent horizontal distance is a bogus concept - apply the cos value to the drop or elevation. 

Why?

if a bullet takes 2 sec to go 1000m it experiences an acceleration (towards the centre of the earth) of 9.8m/s/s for 2 sec.

Whether that 1000m is 'flat' or 'angled' it takes 2 sec to go that far. That's how fast the bullet's going. It can't take less time to cover the distance.

And since it's in the air for 2 sec, it experiences gravitational acceleration for 2 sec. Not some magic lesser amount.

What changes with inclined fire is the relationship between you/the trajectory and the direction of gravitational vector - which, in simplest terms, makes it appear to drop less.

Again, in simplest terms, imagine the 2sec TOF gives a pencil length of drop towards the centre of the earth. Looking horizontally, you can see the full length of the vertical pencil. Look at the vertical pencil from 30deg, and the pencil's apparent length is 0.866 of how it looked from horizontal. Look vertically down on it, and the pencil has zero apparent length, but it's still there.

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Q3: Effect of moving from prone to kneeling.

Some fag-packet maths.

Prone to tripod  raises firer by 50cm-ish.

Prone fire angle was 30deg at 800m which is approx 533mils.

Kneeling changes that by a subtension of 50cm at 800m - or 0.6 of a mil

So, prone angle to target is 533mils and kneeling is 533.6 mils

That is: the prone angle to target is 30 degrees and moving to kneeling changes that to 30.01 degrees.

To say the least, a 0.01 degree change to the angle of fire is not empirically observable at 800m

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Sorry, I was bored 😊

The explanations in fb post made me spill my tea. 

(Jack: 'Show again'!  But, as before - sorry - I was just bored! 😊)

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As I’ve indicated the practicalities of shooting in the UK means in most circumstances holding the lower half of the target will suffice.

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Changing from kneeling to prone in all practical circumstances is irrelevant.

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10 hours ago, John MH said:

As I’ve indicated the practicalities of shooting in the UK means in most circumstances holding the lower half of the target will suffice.

Depends how big the tgt is 😂😊😊

Intended this as ballistic truths 😊

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6 minutes ago, brown dog said:

Depends how big the tgt is 😂😊😊

Intended this as ballistic truths 😊

In the context I’m referring to the targets are big enough with a flat shooting 6XC.

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6 minutes ago, John MH said:

Changing from kneeling to prone in all practical circumstances is irrelevant.

Yup. I gave the maths of it earlier 😊

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As John MH has mentioned there isn’t many cases in the uk you would have to change your firing solution drastically to still achieve an impact. 
I have shot at vallhalla just testing targets and positions and the change was not enough to make a miss if I held low part of plate, 

I have always been a firm believer of use the force (instinct) and apply it to your situation and your firing point. 
I would like some more time at vallhalla to really get first hand experience at advanced angle shooting and really learn more but until then drop a click or two or indeed hold low and use the force you won’t go wrong. 

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Josh - spot on, get experience and confidence in your setup then the slight change in breeze on your face or moving position etc. means you put in 'by eye' small corrections based on your instincts (actually this is a skill set 😎).

Should be no need to adjust, just hold off 'a bit' ( FFP here gives a slight edge IMHO).

BD - I'll accept your 'fag packet' results  - I used 800mm difference between prone and barricade which comes out to just over a mil, so 7 out of 10 for effort! 😄

Jack - hope you did not pay too much for that 'sniper school'? ( that's a leg pull BTW!)

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58 minutes ago, joshmartin8 said:

As John MH has mentioned there isn’t many cases in the uk you would have to change your firing solution drastically to still achieve an impact. 
I have shot at vallhalla just testing targets and positions and the change was not enough to make a miss if I held low part of plate, 

I have always been a firm believer of use the force (instinct) and apply it to your situation and your firing point. 
I would like some more time at vallhalla to really get first hand experience at advanced angle shooting and really learn more but until then drop a click or two or indeed hold low and use the force you won’t go wrong. 

seeing how well you did last year mate and how badly some of the internet shooters have done i'm inclined towards your method , it's easy to make hits when typing at a keyboard but in reality under pressure during the stage most plans turn to ratsh1t and it's the shooters that can react organically under pressure doing it for real that score well. 

and well done young jedi for some brilliant performances last year ! 

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Ronin ... bang on ! 
 

time to fess up to my own stupid school boy error ...

have just rechecked it on my AB elite and have adjusted with the correct data for instance yards instead of meters and the same zero range ..... what a plumb 😳

anyway rechecked it and .....

72B5F115-2A26-471D-88FA-C48781ECC62E.jpeg

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11 hours ago, brown dog said:

Q2:

Equivalent horizontal distance is a bogus concept - apply the cos value to the drop or elevation. 

Why?

if a bullet takes 2 sec to go 1000m it experiences an acceleration (towards the centre of the earth) of 9.8m/s/s for 2 sec.

Whether that 1000m is 'flat' or 'angled' it takes 2 sec to go that far. That's how fast the bullet's going. It can't take less time to cover the distance.

And since it's in the air for 2 sec, it experiences gravitational acceleration for 2 sec. Not some magic lesser amount.

What changes with inclined fire is the relationship between you/the trajectory and the direction of gravitational vector - which, in simplest terms, makes it appear to drop less.

Again, in simplest terms, imagine the 2sec TOF gives a pencil length of drop towards the centre of the earth. Looking horizontally, you can see the full length of the vertical pencil. Look at the vertical pencil from 30deg, and the pencil's apparent length is 0.866 of how it looked from horizontal. Look vertically down on it, and the pencil has zero apparent length, but it's still there.

 

Mathematically, Cosignϴ x C = B

Cosign ϴ x C (C being the hypoteneuse) this is equal to the direct line of sight distance to target = B (in a right angled triangle). B = the actual horizontal distance to the target. This distance B is the distance that the bullet in flight is effected by gravity not distance C.

The distance C is always by mathematical principal (Pythagoras theorem) a shorter distance than B. Therefore the (measurable) effect of gravity on the bullet is only imparted for distance B. 

The rest of your statement is just clouding the issue, the bullet still travels the 1000 mtrs to the target, correct. So the flight time is still your theoretical 2secs, the fact is that, the bullet is only being effected by gravity for 0.866% of the flight, which due to the inclined or declined angle gives a ballistic advantage, the direct result of which is the need to allow for less drop for the given distance. 

It doesn't just appear to drop less, it actually does drop less. Your first line in the question relates to the rule used to determine the horizontal distance to target

The solution posted by Jack is quite right, a simple way to determine the distance to target that should be used with a shooters own dope or a ballistics solver to determine the hold for the shot.

The OPs original intent I am sure was to enlighten new shooters to one way to engage targets at inclined angles.

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Cheetor,

You are confusing 2 things, the 'good enough for deer stalking i.e rifleman's rule, with what BD was trying to explain, also the Op's statement that this is the way it should be done, where more accurately (pun intended) should have been 'used to be done'.

You apply the corrections to your dope for the LOS distance not change the distance and use this 'dope'.

I'm not going to respond any more to this - just go and look it up, have a read etc. there's a lot of folks much clever than me - not as if you are going shooting at present? (start with pages 47-52 applied ballistics for long-range shooting by Litz)

 

TackB -  it's easy to make hits when typing at a keyboard but in reality under pressure during the stage most plans turn to ratsh1t and it's the shooters that can react organically under pressure doing it for real that score well. Concur entirety 😎, hence the dislike for lots of props, too much shite to sort 'at speed' and if a stage allows time for this then IMHO the stage is wrong. 

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"....So the flight time is still your theoretical 2secs, the fact is that, the bullet is only being effected by gravity for 0.866% of the flight, which due to the inclined or declined angle gives a ballistic advantage, the direct result of which is the need to allow for less drop for the given distance. "

How's that? surely the bullet is under gravitational effects immediately it leaves the barrel 

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