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Thread: Why do we have horizontal spread of POI

  1. #1

    Why do we have horizontal spread of POI

    Hi all
    Please go gentle on me as this is my first time.
    I have taken up the engineering challenge of improving the accuracy of RF.

    The question I ask myself is why is there a horizontal spread of the bullet point of impact?
    If everything with our equipment is spot on then the muzzle is stationary while the bullet exits
    I understand we are at the mercy of the Bullet velocity spread even though we may try and mitigate some aspects with engineering so therefore there may still be a vertical spread.

    I can with reasoning alone think of some possible causes but at this stage but have no experimental evidence or experience to prove them one way or the other.

    I would be interested in hearing what other people think may be the reason.

    Graham

  2. #2
    Something I forgot to mention and just to be clear was I was ignoring environmental and human effects.
    Graham

  3. #3
    My first guess would be that everything is not spot on. Even if the equipment is, the ammo is not. Take a look at the Eley analyzer. You're looking at the groups from four barrels and they will have a horizontal dispersion and not always the same. My experience is a test group will follow that graph to an extent. So, you probably have slight imperfections in the bullet, etc. which means that while you might take the human factor out of the picture and ignore that, you can never ignore the environmental factor even if it's inside. That is as long as what you're shooting into contains something (air, other gases, whatever).

  4. #4
    Friend Deveng

    Friend Deveng:


    I was about to shut my machine down for the evening, then saw your posts.

    If there are no human causes, or condition causes, no wind, etc., a Class A RFBR gun with a stopped muzzle has no horizontal dispersion to speak of.

    A Class A RFBR gun, with a stopped muzzle, is only handicapped by the accuracy variation of the ammo.....which is a vertical only handicap.

    ___________________


    Big Dog, and Mary, were at my home today, bringing me some Thanksgiving food....

    Big dog had his targets from down in Dixie, where he kicked out his 2500 with Black Death.

    His last two targets, that were in dead calm conditions, exhibited absolutely no horizontal dispersion, only vertical.

    _____________________

    So no, a Class A RFBR gun with a stopped muzzle, in dead conditions, without human error, has no horizontal dispersion to speak of.

    Only the vertical caused by the velocity variation of our ammo...

    Good question, and thank you for posting.


    Your friend, BC

  5. #5
    Interesting.
    I thought those vibrations on barrel occurred in a circular or an ellipsoid pattern, leading too, to a horizontal dispersion, smaller than vertical thought.
    Then another question rises... if the upper sentence is wrong, why the vibrations only came vertically? What's there to impair the horizontal, or mixed horizontal/vertical ones?

  6. #6

    Friend PedroS

    Quote Originally Posted by PedroS View Post
    Interesting.
    I thought those vibrations on barrel occurred in a circular or an ellipsoid pattern, leading too, to a horizontal dispersion, smaller than vertical thought.
    Then another question rises... if the upper sentence is wrong, why the vibrations only came vertically? What's there to impair the horizontal, or mixed horizontal/vertical ones?
    _____________________

    Friend PedroS:


    Gravity.

    We shoot with our barrels in a horizontal (to the earth) position.

    And to compound matters we float our barrels, they being held by one end allowing the fulcrum principle to magnify the effect of gravity.

    And because of this, horizontal dispersion in a Class A RFBR gun with a stopped muzzle is so negligible, so as to render its effect at the target almost imperceptible.

    Your friend, BC
    Last edited by Bill Calfee; 3 Weeks Ago at 04:48 PM.

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