Sniper scope

[Binnatics]

Playing FC2 I begin to appreciate the sniper rifles more and more. I see a variation of deferently designed sniper scopes and I began to wonder, what are these numbers for?

In the following picture I borrowed from Redraven you can see a beautiful example of a common sniper scope:
[smg id=3648 width=500]

I guess all these numbers have something to do with calculating what a bullet will do with a certain amount of wind, and what it will do from a certain bigger distance. Are there games where these numbers really matter and are necessary to actually hit something from a bigger distance?

And why are these numbers shown in a parabolical way, and not just a straight line?

I don't plan a second career as a professional hitman, but you never know when this kind of knowledge comes in handy :-D

[PZ]

I'm certainly no expert, but it would appear to be more of an elevation scale (used for bullet drop at various distances), and being off-center is because the lines would crowd the numbers too much - just guessing though.

[mandru]

If you had the slug of a bullet and an identical bullet loaded into a high power rifle carefully sighted into a line parallel to the ground and could somehow drop the slug at the same instant the rifle is fired both slugs would hit the ground one slug at your feet the other many thousands of yards away at the exact same instant. 

My understanding is that the "parabolical" contour for the line within the scope is to assist the shooter in compensating for acceleration of drop (a falling object accelerates) for the second before the round hits the ground.  If you know the speed of your round and the range of your target then ballistics can be applied to extend the effective range of the rifle.

[Dweller_Benthos]

If you had the slug of a bullet and an identical bullet loaded into a high power rifle carefully sighted into a line parallel to the ground and could somehow drop the slug at the same instant the rifle is fired both slugs would hit the ground one slug at your feet the other many thousands of yards away at the exact same instant. 

My understanding is that the "parabolical" contour for the line within the scope is to assist the shooter in compensating for acceleration of drop (a falling object accelerates) for the second before the round hits the ground.  If you know the speed of your round and the range of your target then ballistics can be applied to extend the effective range of the rifle.

They did this on Mythbusters - shot a round from a gun and dropped a round from the same height a few hundred feet away, and the round that was fired hit the ground at about the same time as the round that was dropped. They had it timed down to the millisecond, as close as you can come in the real world with things like that.

I also think the scale is some type of guide to compensate for bullet drop, and I never heard of a game where you needed to do this. At least with small arms, but in Battlefield 1942, the tanks had bullet drop, came in handy when someone was just over the top of a hill, you could fire a round just above the hill top and and it would sink in flight and drop on the other side of the hill, that you couldn't see, and hit the target.

[Binnatics]

I read some about ballistics of bullets and there's a lot to count with when you want to predict a bullet's path.
Every good bullet has its BC (ballistic coefficient) and a decent manufacturer gives a BC with the bullet.
I didn't find a solution on the scales in most sniperscopes yet, but I think it's based on the BC of the bullettype used.

The distance a bullet will travel before it hits the ground got many variables involved. So there is off course the fact that the bullet falls (and when you shoot other then horizontal it will fall less hard because the gravity pulls to it under a different angle) and then there is the attrition with the air. This one is influenced by air pressure, wind and even humidity. That will all influence the brake power of the air, and thus the velocity a bullet will keep in a period of time.

So anyway you've got to be a math-teacher to be able to predict where a bullet will hit under certain conditions or you got to have lot of experience I guess 8)

[deadman1]

If you had the slug of a bullet and an identical bullet loaded into a high power rifle carefully sighted into a line parallel to the ground and could somehow drop the slug at the same instant the rifle is fired both slugs would hit the ground one slug at your feet the other many thousands of yards away at the exact same instant. 

My understanding is that the "parabolical" contour for the line within the scope is to assist the shooter in compensating for acceleration of drop (a falling object accelerates) for the second before the round hits the ground.  If you know the speed of your round and the range of your target then ballistics can be applied to extend the effective range of the rifle.

I also think the scale is some type of guide to compensate for bullet drop, and I never heard of a game where you needed to do this. At least with small arms, but in Battlefield 1942, the tanks had bullet drop, came in handy when someone was just over the top of a hill, you could fire a round just above the hill top and and it would sink in flight and drop on the other side of the hill, that you couldn't see, and hit the target.

I know that Battlefield:Bad Company 2 and Battlefield 3 has bulletdrop on all weapons even rocketlaunchers.

[Art Blade]

Binnatics, check this out -- I made a sniper tutorial there for OFP2  :)

[Binnatics]

Thanx Art, that was a good read. I'm stil looking for the reason why they model the 'distance tabs' in most sniperscopes in a curve.
And also, good to see that this OFP game did a nice moddeling on the whole sniper thing. Like Fragger mentioned, they even counted with the fact that most sniper bullets go supersonic.  :-X

[Art Blade]

 :)

Since not all scopes are designed the same way, I suspect it's just a matter of taste/design.

[mandru]

Any falling body follows a curve in acceleration as it drops.  The longer it has been falling the faster it is accelerating.  32 feet per second/per second as I understand it.

Hence the curve.

[Art Blade]

I don't think I, as a sniper, would want to shoot a falling body let alone using a curve in my scope doing that. I'd just wait and watch that somebody fall and then splatter on the ground, saving me one round, grinning.  :-()

[mandru]

In referring to a "falling body" I was attempting to make a general description of a mass under the influence of gravity using the correct language of physics...

Wait!   ????

I'm being Trolled aren't I?  \:/

[Binnatics]

That makes sense Mandru, given that this 'body' is the bullet that should hit the body :-()
But I think the curve would then be:

___600_____500_____400_____300______200_____100______ . ________________________________________
                                                                  _             --   
                                                  --                                 
                                   _                                           
                                                                           
                      _                                                       
                                                                           
 
                                                                       
        _                                                               
       
But the fact is, that in reality (FC2 reality, and the scope used in the beginning of this topic) the curve is the other way around. So that is kind of weird, isn't it ????                                                                 

[mandru]

I notice going back and looking at the original screen shot of the scope that each line of the curve has a number over it after 10 which is probably something obscure like a quick range finder to determine distance by measuring how big a human skull is when viewed through the scope.  Using that theory would put the two bodies in view about 80 meters (roughly 240 feet) out from the shooters position as the dead human's skull looks to be about the size of the space between the 7 and where the 8 is indicated on the index markers.

As the numbers get larger along the curve in question the space from one index line to the next becomes smaller.

I suspect that the index markers curve off to the left to make room to put the numbers over the lines with out the previous index lines obscuring the following numbers.

It would be interesting to find out the actual reason for the reticle markings in this scope's layout.

[nexor]

[smg id=3740]

A PSO-1 telescopic sight mounted on a Dragunov SVD rifle

Spoiler

The top center "chevron" (^) is used as the main aiming mark. The horizontal hash marks are for windage and lead corrections and can be used for ranging purposes as well.
In the bottom-left corner is a stadiametric rangefinder that can be used to determine the distance from a 1.7 meters (5 ft 6.9 in) tall object/person from 200 m (2) to 1000 m (10). For this the lowest part of the target is lined up on the bottom horizontal line. Where the top of the target touches the top curved line the distance can be determined.
The three lower chevrons in the center are used as hold over points for engaging erea targets beyond 1,000 meters (the maximum BDC range setting on the elevation drum). The user has to set the elevation turret to 1,000 meters and then apply the chevrons for 1,100, 1,200 or 1,300 meters respectively.
The 10 reticle hashmarks in the horizontal plane can be used to compensate for wind or moving targets and can also be used for additional stadiametric rangefinding purposes, since they are spaced at 1 milliradian intervals, meaning if an object is 5 m wide it will appear 10 hashmarks wide at 500 m.
This reticle lay out is also used in several other telescopic sights produced and used by other former Warsaw Pact member states.
The PSO-1 reticule can be illuminated by a small battery-powered lamp.

[Binnatics]

Thanx a lot Nexor, that explanation deserves a slap on the back!  :-X
It's just what I was curious for, and a very precise explanation in fact!

So the curve shown on most scopes is just a helpful tool to determine the distance to the target. And the extra chevrons below the headmarker are to compensate a bullet-drop bigger then the pre-calculated bullet-drop caused by a distance of 100 meters.
In fact, the scope is designed for the rifle + bullettype. Only with larger distances (larger then 1000 meters), these extra chevrons are helpful.

Urhhmm, so in fact, when you try to snipe someone at a distance of 200 meters, you should hold his head above the main chevron, to compensate the prefab compensation, right? :-()

One more question:

The PSO-1 reticule can be illuminated by a small battery-powered lamp.

Why would someone want to illuminate the scope?

Edit:
:ideas :knockout Stupid me, you mean the actual drawings inside the scope, can be illuminated. Like glowing lines, instead of black lines, for night snipering.

[Binnatics]

Funny, if I go pack to the original image I can determine that, since the 2 creatures laying on the ground seem to be 1,8 meters tall, Redraven must have sniped them from a distance of, let's say 1100 meters ^-^ :-X

[nexor]

probably yes, and you are correct about the light, it illuminates the markings at night

[fragger]

Good explanation nexor, cheers :) :-X

All that scope detail is superfluous in games, with the odd exception like OFP 2 (going by Art's rundown - I haven't played that one myself). Looks good but doesn't actually do anything. It's always a case of put the centre mark on the bad guy's head and pull the trigger. No bullet fall, travel time or windage... Unrealistic but fine for games like FC2 where the emphasis is on action rather than fiddly technicalities, such as being able to fix any engine problem with a few twists of a socket wrench on top of a radiator, or healing any gunshot wound with a jab of a needle :-()

[PZ]

Good one - looks just like my Dragunov  :-()

[Art Blade]

thanks, nexor, for that nice explanation :)

oh and mandru.. teehee  :-D