Realistic ballistics & zeroing rifles

[RCMoonPie]

Gravity pulls all the time. The round is always effected by gravity... If you fire a round horizontally and drop one from the same height, the rounds will hit the ground at the same instant. With slow moving round, gravity has more time to act upon it, pulling it down far more then a fast moving round. The same thing applies with wind from the side. You need to compensate for wind far more with a slow moving frisbee then a speeding bullet.

EDIT: Speed is not synonymous with force, some would say like you and being a physicist.

No...wind resistance does not change the constant force of gravity.

Yes the force of gravity is a constant.
But....the speed/velocity of a round changes from the point of triggered fire until it it lands.
It leaves the barrel at maximum velocity and slows over distance due to resistance, making it vulnerable to the constant pull of gravity.

Your bullet drop scenario is very incorrect as well.
I will keep it as basic as possible so you can follow along.
A 50 cal round can be placed on target at distances of 2+ miles away.
The Barret M82A1 has a maximum range of 6800m.
1m = 3.2808 ft.
1 mile = 5,280 ft.

So...
6800m = 22,309.44 ft.
22,309.44 ft. = 4.225 miles.

So a 42.8gram 50cal. projectile, powered by a 660 grain load, traveling at 2,850 ft. per second....would take 7.827 seconds to travel a distance of 4.225 miles.

7.827 seconds

Since gravity is constant, and exudes its force on all objects regardless of size, shape, or weight...any two objects can be dropped and will fall at the same rate. For instance, I could drop a bowling ball and an ink-pen and they will hit the ground at the same time. The only factor is wind resistance. This is what keeps a feather aloft when dropped. If the feather and bowling ball were dropped in a vacuum...they would strike the floor simultaneously.

7.827 seconds

With that...you can take any object with any mass, with little to moderate wind resistance...and drop it anywhere from a height 6 or so feet, which would be the height of Joe Average shooter...and time the drop to see how long it takes to hit the ground after release.
Try it...I'll wait.
Okay? It takes a little over 1 second from release to hitting the floor.
Thats quite a bit less than 7.827 seconds wouldnt you agree?

This proves that the speed/velocity of a fired round is indeed a greater force for a matter of seconds, than that of gravity.
Once speed declines, the bullet's becomes effected by the constant force of gravity.

How do you think Rockets are able to travel into outer space?
The thrust from the rockets are far greater than gravity's pull.
This thrust remains constant and directionally upward so the initial speed is slow....until the rocket is free of earths gravitational pull. It explains why you cant throw a baseball into outer space. The baseball when thrown straight up, starts out with enough power to leave the pull, but loses velocity, loses momentum, and then becomes subject to gravity and falls back down to the ground.

Physics are definitely involved...as well as basic math.
Maybe you should study both before you post again relating to this subject.

Edit: I want to point out to all...that I meant no disrespect to nedlands1, nor was I trying to be "condescending"...at least no more than his post was. LOL

[KP]

That's because the .50 cal round is not fired straight ahead, but upwards, so that it falls down into the point of zero.

fail

Epic fail.

[BloodBane611]

The Barret M82A1 has a maximum range of 6800m.

Your whole experiment is mixed up. The Barrets maximum range is 6800m. That is not its range when the rifle is pointed horizontally and fired, that's when exerting a huge amount of its force against gravity. Good try though.

*EDIT* and KP beat me to it.

[$kelet0r]

RCMoonpie, I normally would not interject in a thread like this as I have no modding skills to offer ... but you exhibit a shocking lack of understanding about ballistics and physics in certain critical aspects. Advise you sit down, think through and work out why you're wrong ...

[RCMoonPie]

Its the maximum range point to point...not maximum effective range.
Of course it is fired horizontally....firing the weapon vertically would have little effect on a target.
Either way...regardless of the elevation of the weapon....the point still stands....and you stated it as well Bloodbane....the exertion of force is greater than that of gravity...as with all ranged weapons.
If it weren't, the bullet would exit the rifle and land at our feet....this is most obvious.

No way around it....the drop example stands as well.
Even at the max efective range....which is much shorter...the dropped round from 6ft still strikes the deck before the round strikes the target. Period.

I am more than willing to admit when I am wrong
But the numbers dont lie.

Why dont you nay-sayers show your examples....and your math....and prove me wrong.
Oh wait, I get it....its easier to be flash a creative insult on a forum and just say "your wrong" with no practical argument.
Makes sense.



Edit.....one could argue that the end result would be different if the weapon were fired straight up into the air, that if maximum range were reached. The time for the round to fall back down to the earth will basically double.
But one must take into account other perameters for that scenario, that maximum range is reached, hang-time if any, acceleration from the temporary "suspension", time to reach terminal velocity, versus distance left to fall. Also the fall isnt excellerated by propullsion, as it is falling under its own weight at the constant speed of gravity at this point.

[KP]

It has to be done:





If fired horizontally, the bullet will hit the ground in the same time as if it was dropped, no matter how fast it goes. If fired at an upwards angle - as you have to do to hit something that far away (not that I think that 6800 metres is the max. effective range, considering that the world's longest kill was at about 2400) - it will take longer to hit the ground.

[RCMoonPie]

I like mine better...


The Blue line above the rifle shows the site allignment, and the blue line at the rifle's compensator shows the sight on target.
The red line shows the path of the round when it leaves the barrel.

Diagram A shows the M16A2 zeroed at 300 yards.

Diagram B shows the M16A2 zeroed at 300 yards, but being fired at a target 500 yards away. The arc of the round is exagerated for demo purposes.

Diagram C shows the M16A2 zeroed at 300 yards, but the rear sight has been adjusted and "clicks" added for accuracy at greater distance. The clicks were based on a known distance. The zero doesnt change, just the elevation of the barrel as a result of the sights being adjusted for range. 1)shows the adjustment to the site 2)shows the lowered butt of the weapon as a result of rear-site adjustment 3)shows the raised elevation of the barrel as a result of the adjusted sight and lowered butt.
* annotates the adjusted (and exagerated) position of the adjusted site.

Diagram D shows the strike of the round from an M16A2 zeroed at 300 yards, on a target at a shorter distance.

I think we are still saying the same thing though!

Now if you, Bloodbane and I could just agree on those dang bridges! LOL

[RCMoonPie]

If fired horizontally, the bullet will hit the ground in the same time as if it was dropped, no matter how fast it goes.

I see....because you say so.
You can argue like a child until you are blue in the face.
But until you prove your theory....you are just blowing smoke.

The numbers dont lie.

[OkitaMakoto]

Gravity Concepts and Applications

Common misconceptions about guns:
A dropped bullet will hit the ground before one which is fired from a gun.
As shown in the illustration of a horizontal launch, gravity acts the same way on both bullets, giving them the same downward acceleration and making them strike the ground at the same time if the bullet is fired horizontally over level ground.

Take it how you want it, thats the first link I found. Is this the part where I say illustrations don't lie?

Now, I have a question on your diagram, and this is purely me wanting to know. but wouldn't a rifle zeroed to 300 yards, when aimed at a 100 yard target hit above the point of aim? Since the rifle is zeroed for more drop[300] than what is being fired to?

I also love how some of your diagrams bullets travel straight and then plummet, while others start curving. The bullet is affected by gravity the moment it leaves the support of the bottom of the barrel. There's no if ands or buts about it.

[RCMoonPie]

If this website is correct, and I have no reason at this point to doubt it....I was wrong.
Gravity Concepts and Applications

I said....if I am wrong....I would gladly admit it.

Edit....OkitaMakoto beat me to this!
In regards to my drawings...all I did was cut and paste some objects and draw some lines.
Same as some posts I was referencing...it wasnt drawn to scale and was just demonstrating my thoughts on the subject to poke at Jonny.

[ReadMenace]

RCMoonpie: Monkey Gun

You are wrong, you need to be honorable here and admit it. If you can't find the maturity to do this, you should atleast leave these guys alone so that we can benefit from their work.

-REad

[RCMoonPie]

RCMoonpie: Monkey Gun

You are wrong, you need to be honorable here and admit it. If you can't find the maturity to do this, you should atleast leave these guys alone so that we can benefit from their work.

-REad

Um....you need to go back and read a couple of posts back, jack-hole.

Project Reality Forums - View Single Post - Realistic ballistics & zeroing rifles

This is ReadMenace's first post in this entire thread.....and now he comes along to finger point and preach about "honor" and "maturity" after the fact when I have already said I was wrong?

This is why most folks never want to admit fault in here and just argue.

So....who is next?

[ReadMenace]

In your post, you do not concede that you're wrong, you propose that you may be wrong if that site is correct. The site is correct.

-REad

[OkitaMakoto]

In your post, you do not concede that you're wrong, you propose that you may be wrong if that site is correct. The site is correct.

-REad

If this website is correct, and I have no reason at this point to doubt it....I was wrong.

Drop it Read. When a man admits he's wrong you don't try to beat him with technicalities. He admitted he was wrong. He said if that site is correct[and said he has no reason to think it is wrong] then he was wrong.

Lay off.

[RCMoonPie]

oh dear God...are you kidding me?

"If this website is correct, and I have no reason at this point to doubt it....I was wrong."

[ReadMenace]

Dropped.

-REad

[nedlands1]

Project Reality Forums - View Single Post - Realistic ballistics & zeroing rifles
:d uh:

I'll say this, you are probably right about me needing to study more, but having said that there is a chance that I have studied more than you (going into second year of chemical engineering at uni).

• I did not imply that "wind resistance does not change the constant force of gravity". I merely provided an example of how the longer a force is applied to an object the more it will accelerate away compared to a similar object with a force applied to it for less time (ie greater impulse). Think of it this way. A bullet in the air experiences a gravitational force. Force is an acceleration of mass. Assuming that no other forces are acting upon this bullet (ie drag), the bullet will accelerate at 9.81 m/s^2 into the ground(acceleration due to gravity at earth's level approximately). The more time a round has is the air (ie a slow bullet as opposed to a fast bullet), the more time it will have to accelerate. The more time it has to accelerate, the greater velocity it has. The greater the velocity it has the more it has moved. The more it has moved downwards, the more it has "dropped". A practical example, the more time you hold your car's accelerator down the more distance it will travel, all other things the kept the same.

• You mentioned that the round loses velocity when it leaves the barrel. Your own calculation is way off then as it assumes the horizontal velocity is constant. Nice work

• You then mention that the round will take, "a little over 1 second". This is plainly wrong. Using constant acceleration equations and assuming drag is minimal (drag is proportional to speed and surface area perpendicular to direction of travel (amongst other things), both of which are very small) and the round is fired horizontal, you get the time as being 0.62 seconds (t=(2d/a)^1/2, t= (2x1.87/9.81)^1/2, t=0.62 seconds). I also went and followed your suggestion to drop something from about 6 feet. It took about the same time as what I calculated. Not "a little over 1 second". As you aptly said, "Physics are definitely involved...as well as basic math".

• Again you are comparing apples with oranges with "speed/velocity ... force". This cannot be done. Speed and velocity are different things to begin with. Force as another thing altogether (speed: distance per change in time, velocity: distance per change in time in a particular direction and force: mass times distance per change in time squared in a particular direction [F=ma=mvt^-2]). The only forces to really consider are drag and gravitational (once the round has left the barrel). Both of which are generally acting in a totally different axis (horizontal mostly and vertical). The drag force actually help keep the bullet in the air and it increases as the bullet changes from traveling horizontally to into the ground.

• The force of the propellant gases provides greater force than that of gravity. Yes I agree but where I disagree is how you think that that it somehow counteracts gravity when you fire a bullet horizontally. Dude you cannot do your sum of the forces on two forces (gravity and propulsion) and say that one is counteracting the other if the forces aren't even in the same axis. Gravity acts downwards. Gun shoots horizontally. Downwards is perpendicular (therefore not in any shape or form in the the same axis) to horizontal.

Before anyone else bags RCMoonPie. I'd just like to say that regardless of the little tiff, he has made some good points about other things and has shown some good insight.

[KP]

Good man. Now let's get back to the epicness of mathematics and ballistics.