flight trajectory and "miss" calls

Discussion in 'ELR, Ballistics & Bullets Board' started by cj8vet, May 16, 2018 at 9:07 AM.

  1. cj8vet

    cj8vet

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    2 questions-when talking long range flight--say greater than 750-- 1000plus, is the bullet pointed down as it "lands'impacts the target? --I see "angle" in the impact material/frames but someone tried to convince me the bullet was pointing level or up as it came down--i think it is point down--

    2ndly-calling misses--with the extreme arc of the flight- it seems that just because 2 strikes are say 3 MOA apart on the vertical target, that is not necessarily a 3 MOA correction? am I way off??
    any good references for this topic?
    Thanks
    Mark
    cj8vet@gmail.com
     
  2. dkhunt14

    dkhunt14

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    The spin should keep the bullet point level. If you look at holes in a target at 1000, they are round if the gun is tuned. It the bullet is entering point down the holes would be oblong.

    3 MOA is alot for 1000 yards. That's 30 inches. Conditions could be some but I believe that much has to do with the accuracy of the gun. Matt
     
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  3. retired

    retired

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    it depends a ton on the actual load and the actual distance.
    specifics

     
  4. fivering1

    fivering1

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    The gyroscopic effect on the spinning bullet keeps the axis of the bullet in line with the rifle barrel it was fired from. The bullet does NOT act like an arrow which has fins at the rear.
    If the rate of spin is insufficient the bullet can start wobbling, often at the velocity zone where it drops below the speed of sound, and can become very inaccurate. That is why different bullet lengths and weights have different recommended twists. Longer bullets require faster twists, as a result of upward air pressure on the nose of the bullet during flight.
     
  5. dkhunt14

    dkhunt14

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    If this was true the holes in paper would be oblong. I believe the spinning and the air levels them out When they settle. When the load and gun are working the bullets are stable and the holes get smaller at 1000. Some guys measure holes to see if they are tuned. My holes are round and not elongated. Matt
     
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  6. barefooter56

    barefooter56

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    http://www.appliedballisticsllc.com...ransonic Effects on Bullet Stability & BC.pdf. Bullet length also affects the barrel twist rate required for stabilization of the bullet.
     
  7. SteveOak

    SteveOak Silver $$ Contributor

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    Let's start with a hypothetically perfect scenario.

    We have a perfect barrel. The outside is round and true. The bore is perfectly round and concentric to the outside diameter. The bore runs straight through the center of the barrel. The barrel is pointed perfectly at a .001" dot that is 100 yards away. There is no wind, no mirage, no heating effect of the air, the only things that will affect the flight of the bullet are the resistance of the air as the bullet flies through it and gravity. Magically gravity does not affect the barrel so it has no droop. The barrel is in an ultimate Benchrest rig so that it is perfectly aligned to the dot on the target.

    The bullet fired from this barrel will miss the target because gravity will cause the bullet to drop slightly.

    To compensate for this we will raise the muzzle. The bullet will now leave the barrel in an upward direction.

    As we increase the distance, 200 yards, 300, 400, 500, 600, 1,000, we will need to increase the upward alignment of the barrel to compensate for the effects of gravity so that the bullet hits the dot on the target.

    At each of these distances the bullet, as it passes through the target, is not perpendicular to the target, yet as long as it is adequately stabilized, it does not make an oblong hole in the target.

    This is because (and I am oversimplifying here, the actual attitude, rotation, nutation, precession and so on are quite complex) the bullet is generally aligned to it's flight path. When the flight path is upward, the alignment of the bullet is generally upward. After the bullet passes the apex of its trajectory, the path of the bullet will be downward and the alignment of the bullet will be generally downward.
     
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  8. retired

    retired

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    and the end angle is pretty steep depending on distance and load.

     
  9. spclark

    spclark Gold $$ Contributor

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    Whoo boy you must have pulled 1,000 yard targets for black powder shooters & lived to tell the story! Talk about ‘INCOMING:eek::eek::eek:
     
  10. damoncali

    damoncali Gold $$ Contributor

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    The bullet very closely tracks the trajectory. The bullet is angled slightly down at 1000 yards.
     
  11. fivering1

    fivering1

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    You could not be more wrong.
    Do some home work before you spread more wrong information.
     
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  12. damoncali

    damoncali Gold $$ Contributor

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    You sure about that?
     
  13. retired

    retired

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    you have made a poor generic reply with no know ballistics other than 1000 yds.
    to late to make up a story to cover your butt.

     
  14. damoncali

    damoncali Gold $$ Contributor

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    Is there a thread you won’t ruin? You are one miserable sob.
     
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  15. retired

    retired

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    you continue to ruin threads with replies with no thought, no data. do not point the finger at me. i pointed out the issue very early.
     
  16. SteveOak

    SteveOak Silver $$ Contributor

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    Well, this is not artillery we are talking about. :)
     
  17. retired

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    i will go back to my original answer.
    it depends on the load and the distance.
    neither have been listed by the op.
     
  18. Ballisticboy

    Ballisticboy

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    I am afraid this is completely wrong, correctly working gyroscopic stability attempts to keep the bullet pointing in the direction of the relative airflow over the bullet, not in the direction of the barrel. As soon as the bullet leaves the barrel it will change the angle in which it is pointing due to the initial yaw and yaw rates present on all bullets as well as the effects of any cross wind and gravity. This means the bullet will not be pointing exactly in the direction of the relative air flow (made up of the bullet horrizontal and vertical movement and the wind direction) and will thus be subjected to an aerodynamic pitching moment. The gyroscopic response to the aerodynamic pitching moment will be to yaw the bullet at a small angle in a direction at 90 degrees to the initial angle. This in turn will produce a new aerodynamic pitching moment to which the gyroscopic response will be to reduce the initial yaw angle. It is this feedback system which enables gyroscopic stability to work in attempting to keep the bullet pointing into the relative wind direction. It's effect is exactly the same as static aerodynamic stability and thus it works exactly like fins.
    Due to gravity the bullet will start to accelerate towards the ground immediately it leaves the barrel. This gives the familiar trajectory curve and changes the direction of the relative airflow. The gyroscopic stability will make the bullet try to follow the curve of the trajectory due to the change in direction of the relative airflow. Thus, at any range the bullet will always be pointing down relative to the direction in which it was first travelling. Towards the end of the trajectory near the target, assuming the target and the rifle are at the same height above sea level, the bullet will be pointing down towards the ground since the trajectory direction and thus bullet direction of flight will also be downwards. The angle will be dependent on the range and bullet velocity but will normally be small at rifle ranges.
    It will not produce an elongated hole in the target as the target is relatively thin and the bullet is pointing in the direction in which it is travelling.
    The easiest accessable reference material is McCoy's book, though a better explanation is in the UK produced Text Book of Ballistics.
    There have been projectiles which, due to excessive gyroscopic stability, have stayed pointing in the initial launch direction in a deliberate attempt to produce aerodynamic lift and thus to flatten the trajectory curve. These projectiles have displayed horrendous wind sensitivity and very poor accuracy and precision. You would definitely not want to fire such a projectile from your rifle.
     
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  19. TUFFLUCK

    TUFFLUCK

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    Barefooters post is the one of the few posts in this thread to read and reread.

    Bryan Litz has some excellent references (look in Chapter 10 in the the included link) that will specifically address your question.

    http://a.co/5UzdOMo
     

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  20. cj8vet

    cj8vet

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    sorry for the un clear questions and the subsequent arguments. I should have stipulated "generic question""Generic load"-in my case 6BRX 105 Hybrid.-around 1000 yds. The 3 MOA was a random number. see attached pic for the general question-is 3 MOA at the target really 3 MOA scope correction?(measuring on an arc, not a straight diverging line) maybe it was answered and I am too dumb to see it. I know there are a gillion factors involved. Then the "calling miss" question was with respect to these arched in rounds impacting ground "X" feet behind or in front of Prairie dogs and converting that into MOA calls.
    Thanks for your patience and consideration,
    Mark moaarc.png moaarc.png
     

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