Need A Knowledgeable Explanation......

Sunray, I have seen many rifles that were boresighted with a device, and not be anywhere close to zeero at 25 yards.
Boreighting with a device will generally get you good for windage, but not always for elevation.

This is why I like to look down the bore at 100 or 200 yrads and go from there.
with the system I described I put to rifles on at 100 yards in 2 shots each, last Monday.

It is a very simple thing to do, and a lot easier to do at 100 yards than at 24, because the distance is easier to adjust for.

Cat
 
I knew (from what little I know....) that I would be high at 25 yards. So I thought I would be on paper at 100.

40 inches high.......?!?! Yee ikes!

My windage was pretty well on.

Thanx for the info guys. Gonna go back with a rear rest and fine tune my groupings before I re zero my turrets. I was finally hitting (around) the center of the target, before the range closed.

My groupings weren't consistant because of movement, and some flinching. Gonna have ta work on that...
 
As a bit of an aside, a bullet in flight does indeed TRY to climb...at least, the nose does. Much like an airplane wing. As it exits the muzzle the nose trys to climb as a airplane wing at speed will do, but this is quickly overcome by the gyroscopic force of the rotating bullet (on each revolution). Its ONE of the reasons that for a lot of a bullets flight, it "nods" or yaws. Its also the reason that a tumbling bullet, tumbles. If an average lenght/weight bullet for a given caliber were fired horizontally, from a unrifled bore...upon exiting muzzle, the nose would begin to lift. With no rotational forces to overcome this lift....the bullet begins to tumble. I think everyone here is in agreement however, that this minor amount of bullet nose lift could never overcome the rotational forces of a spinning, stabilized bullets or gravity. If gravity forces were removed from the side of the bullet(firing either straight up or down), one might see at very long range, the bullet begin to depart from the line of sight. theoretical to be sure.

The problem this fellow is having though is almost certainly a proble with scope mount, scope or receiver in that order. I have seen dramatic problems with low cost scopes but this sounds almost like the scope and bore are looking in 2 different directions. If this was one of those rifle/scope combos where they put the cheapest Bushnell/Tasco scope on, could be that the porper effort was'nt put into mounting scope. I had a similar problem one time with New rem700, new B & L scope, new Leupold 2 piece mounts. Mounted but not tightened, rear of scope was about 1/8 inch off seating in rear ring. Bought another set of rings, same thing. Sent it back to rem. As unbelieveable as it might seem, nothing wrong with rifles receiver...does got 2 bad sets of scopes mounts. Not common but it happened to me. I wonder if dealer that mounted scope tightened both rings at one time. Its possible to torque down a scope into rings/mounts that don't really fit properly.
 
I guess it depends on what you are comparing it to. A bullet does not climb in relation to the bore axis, however it does climb relative to the shooter (in most cases) and relative to the target (in most cases). that's what most people are talking about when they are talking about bullets climbing. To most people the axis of the bore means nothing, and for all intents and purposes it does mean nothing. You need not even be aware of the bore axis, so long as you know how to work a scope. Yet people are quite aware of their position and their targets, and know that the bullet must go higher than the target (and often the shooter) in order to arc down into the target as desired. this involves the bullet gaining elevation, which as far as I know means the bullet CLIMBS. the only instance where this might not occur is when shooting downhill.
 
The bullet does not "climb" perse, but IS launched on an upward trajectory.
Think Mortar, archery or artillery.
It needs to 'rise' to counteract the 9.81m/sec2 gravitational constant.
Hence the curved trajectory.
 
Dosing said:
The bullet does not "climb" perse, but IS launched on an upward trajectory.
Think Mortar, archery or artillery.
It needs to 'rise' to counteract the 9.81m/sec2 gravitational constant.
Hence the curved trajectory.
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I agree with Dosing and others on this, the bullet does indeed start to drop the moment it leaves the muzzle due to the constant gravitational forces imposed on it. The scopes reticle is only a means of accurately intersecting it's line of flight. Adjusting the point of impact at 100 yds is a means of identifying its arc for its second intersection with your line of sight at a distant target.

Randy Carriere wrote:
As a bit of an aside, a bullet in flight does indeed TRY to climb...at least, the nose does. Much like an airplane wing. As it exits the muzzle the nose trys to climb as a airplane wing at speed will do, but this is quickly overcome by the gyroscopic force of the rotating bullet
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Sorry Randy, not to get too complicated but the reason the planes wing causes lift is because the surface area on top of the wing is greater than the surface area on the undeside of the wing, simply put this causes lift. If the top and bottom of the wing were symetrical it would not cause any lift, notice how a plane increases it's wings surface area when slowing down to land in order to increase it's lift because of the lower speed required for landing ( you might have seen this when a plane extends it's wings during take off and landings)!
The rotational force of the bullet is what stabilizes it in flight by spinning around it's center of gravity just like when you spin a football when throwing it otherwise it would start to yaw and tumble and loose it's stability in flight thus causing it to quickly fall to the ground, this has nothing to do with gyroscopic forces. The bullets flight path is controlled by the angle you set the rifle in relation to the scopes axis, this defines it's trajectory.
The scopes reticle or assembly that holds the reticle is never moved but rather the scopes body is moved off axis that is what causes the muzzle to rise or fall since it's the scopes body that is attached to the rifle! I hope I am not too confusing. :)
my .02
bigbull
 
Big bull, you make some interesting points. Your example of a football that was not spinning would begin to yaw. What force would cause this yaw? Gravity would act on both the front end and back end equally...what would cause it to begin to tumble(yaw)? I'm not an expert and like everyone else I take what I experience and what a read/hear/see and try my best to understand. I understand the principal of a high pressure area/low pressure area above and below an airplane wing and that this causes lift but, a toy balsa wood plane for example....the wing surface is not curved is constant and is the same on top as on bottom yet it still lifts when one releases the rubber band? You make an interesting point though. A site that has interesting info on these types of topics is:

http://www.steyrscout.org/ballisti.htm

Go to the bottom of page and I guess just check out the items highlighted in blue. Some of it can be pretty dry reading but might be of interest to many here. Always interested in learning more from my fellow gunnutz. :D
 
Randy Carriere said:
Your example of a football that was not spinning would begin to yaw. What force would cause this yaw? Gravity would act on both the front end and back end equally...what would cause it to begin to tumble(yaw)?
:D
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Randy, the balls inability to spin rapidly enough on it's axis would cause it to destabilize due to the wind resistance and eventually cause to to tumble around it's "center of gravity". An object always spins around it's center of gravity unless it has a rotational force acted upon it that would cause it to spin on an axis like barrel rifling has on the jacket of a bullet, this centrifugal force causes it to overcome its tendancy to tumble from the wind resistance and keeps it spinning and pointing forward until a point and time when other forces overcome it. It's ballistic coeficcient determines it's wind resistance and therefore its flight time to any given target, the shorter the flight time the less it drops (shoots flatter because of less gravitational effect), the less speed it looses the greater the impact speed (power/energy), the two factors always acting upon a bullet are wind resistance and gravity.

As for the toy balsa plane, I can't say.
bigbull
 
It seems the more this is discussed, the more confusing it becomes. Yes an unstable object tumbles around its center of gravity(football or bullet), I do'nt believe I said otherwise. I'm talking about what initiates the yaw in the unstable object. If an unspinning football begins to tumble due to "wind resistance", would'nt that same wind resistance be the thing that causes a unspinning bullet to start tumbling. If wind resistance is lifting nose of football over and begins the tumble, then our different opinions seems to be, what your calling wind resistance, I'm calling lift. If either spins fast enough then instability due to wind resistance or lift is'nt a problem...I believe thats what I said in my original comment.

Your point about lift not being possible because head on profile of bullet is symetrical unlike an airplane wing is a good one. But if the symetrical wing profile of the imaginary balsa wood plane produces lift, why would'nt the symetrical bullet profile do the same thing? It goes without saying that if both are spun fast enough that wind and gravity are the major forces acting on the bullet.
 
I have to agree with Slavex a bullet does climb. when a bullet leaves the barrel , its trajectoy can be devided into a vertical and a horizontal velosity. If the bullet is fired parrelel to the ground it will have no vertical velosity and only a horzontal velosity at the moment it leaves the barrel,at witch point gravity takes hold and starts to pull the bullet down now giving the bullet a negitive vertical velosity.However if the bullet is fired upward as when fireing at long range the bullet will have both a vertical and a horizontal velosity and will be climbing until the force if gravity over comes its vertical velosity ,at which point it will start to fall,
 
If the bullet is fired parrelel to the ground it will have no vertical velosity and only a horzontal velosity at the moment it leaves the barrel,at witch point gravity takes hold and starts to pull the bullet down now giving the bullet a negitive vertical velosity.
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That statment is correct.

However if the bullet is fired upward
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This is exactly what you have to do to get the bullet to stike, point of aim at any given distance. The line of bore is above the line of sight. You are firing the bullet upward. The bullet itself can not exit the barrel and climb unless the barrel is bent.

When firing long range (.308 at 1000 yards) the line of sight is at the target (target sights or scope).
When looking at the shooter from the side, you will see that the barrel is slightly pointing up. The bullet is being fired upward to elevate the trajectory (big curved flight of the bullet)in order to hit the target. The highest point of the trajectory of the bullet will be 20 some feet above the line of sights. The bullet is being fired upward, not climbing from the force of being fired.

If you ever get a chance to see guys shooting blackpowder cartridge at 1000 yards they are point the barrel upwards at a greater angle, but the line of sight is parallel to the ground.
 
Randy Carriere said:
Your point about lift not being possible because head on profile of bullet is symetrical unlike an airplane wing is a good one. But if the symetrical wing profile of the imaginary balsa wood plane produces lift, why would'nt the symetrical bullet profile do the same thing? It goes without saying that if both are spun fast enough that wind and gravity are the major forces acting on the bullet.
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The bullet will begin to tumble to some effect, with or without air resistence if the projetile is not yaw controlled in some manner. In the case of a bullet the rifling provides the spin to stabilise it. Otherwise the launching from the barrel itself with provide an uneven stability, along with the muzzle blast. I can't think of how to explain it shortly, so I'll pass.

Lifting. Why doesn't the bullet lift itself. Well simply put the bullet is symetrical over its ENTIRE body, so for any upward effect the 'bottom' (part facing the ground) gives you, you will have a downward force generated by the 'top' (the part facing the blue sky and puffy little clouds).
The two cancel each other out.
The plane and wing are in opposition to each other is some effect. The wing is there to lift the plane, if you made the PLANE symetrical, with a second wing pushing down, no flight. The wing, and its semitry or lack thereof is not the issue, its the wings relation to the airplane. The bullet has no wing, just itself.
Even a self-lifting body still has to have something to act for, without counterballancing the lifting effect of the lift generating portion of the body.

With the bullet being symetrical, any 'lift' gets cancelled by the opposite side of the bullet.


Now, in theory, if you shoot a round ball, and catch it ever so slightly at the muzzle, to impart spin.....
 
so when I go up a set of stairs I am not climbing? when I go up a ladder I am not climbing? to ascend or gain altitude or rise are all versions of climb. And a bullet most definitely does these things when it is fired in an upward direction. as GrensVegter details a bullet is in fact climbing, even while losing velocity until it reaches the peak of it's arc and then begins it's downward descent.
 
when it is fired in an upward direction
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"Fired in an upward direction" is the key phrase. The bullet is not climbing by itself when it is fired, you are in fact pointing the barrel in that direction, in order to hit what you are aiming at.

Lets go about it, this way.
Shoot a lazer through a barrel that is absolutely parallel to the ground. Now set up targets with this same lazer through the barrel at 500 yards, 300 yards, 200 yards, 100 yards 50 yards, 25 yards and 1 yard, from the muzzle. All right on the center of the target. Fire a shot without a sight, just with what you have lazered through the bore. The shot at 1 yard will be right on, 25 yards would be slightly lower but may not be enough to measure, 50 yards will be lower again, 100 lower again. At each distance the shot will be lower. The shot will never be higher then it was at 1 yard.
Agree???Nod your head up and down :?

So please tell me, at what point of the trajectory does the bullet starts to climb :eek:

This is a great debate :mrgreen:
 
traj.gif


Study the picture.

I think the confusion is in the wording. If you launch the bullet upwards it will climb above the line of sight.(cuz that's where you launched it!) The bullet will never *climb* above the bore centerline no matter how high you aim. The bullet will always start falling when it leaves the barrel.

Clear as mud, huh? :wink:
 
joe-nwt said:
traj.gif


Study the picture.
quote]

Thanks joe, that picture is exactly what happens. The rifles angle is changed to change the point of impact in relation to your line of sight, simple :D
bigbull
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who cares what it does in relation to the bore axis? it's elevation changes, that's what happens, that means it climbs.
 
Slavex said:
who cares what it does in relation to the bore axis? it's elevation changes, that's what happens, that means it climbs.
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No it doesn't "climb" in relation to the bore axis, joe is right! :eek:
bigbull
 
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