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Change POI with yardage increase?

Discussion in 'Shooting Related Threads' started by yakimaman, Apr 22, 2012.

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  1. yakimaman

    yakimaman Active Member

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    Was talking to another shooter and he was telling me that you should add comb height as you move back in yardage. Shoot singles then add washers to your comb to raise your POI for the hcp round. Doesn't make sense to me, but I've been wrong before. Can that be right?

    rm
  2. hmb

    hmb Active Member

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    Depends on the gun, high rib or low rib makes a difference. Unsingle or top single makes a difference. POI tests at the patterning board is the way to tell. HMB
  3. BigM-Perazzi

    BigM-Perazzi Well-Known Member

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    K.I.S.S the true secret to trapshooting...
  4. b12

    b12 Active Member

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    I don't change anything. It seems the afarther I get back the lower I point on the bird. Just works for me. But I prefer a flatter shooting set-up. 60/40 the most for me. wild bill
  5. Setterman

    Setterman Well-Known Member

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    See the thread above.
  6. E. Beaver

    E. Beaver Member

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    If you break your singles target 17 yards from the trap house the distance to the target is 33 yards. At 20 yards the distance would be 37 yards, and at 22, 24 and 27 yards the distance would be 39, 41 and 44 yards respectively.

    With your comb set for singles to be 6" high, the shot drop at 20, 22, 24 and 27 yards would be 0.7, 1.3, 1.6 and 2.4 inches.

    My comb height for 16, 20, 22, 24 and 27 yards is: .250, .350, .400, .450 and .500 respectively.

    A .062" spacer will give you about a 2" rise in your point of impact.

    Raising the comb as you increase your yardage is to make up for shot drop and that it takes longer for your shot to reach the rising target.

    Your mileage may vary.

    Charlie
  7. E. Beaver

    E. Beaver Member

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    Check out the "why a high POI required" thread and be sure to read Terry Jordans April 23 post.

    Charlie
  8. timb99

    timb99 Well-Known Member

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    Some do, some don't.

    Some folks like to find a "happy place" where they are satisfied with their POI height setting at handicap yardage, then "learn to shoot" a high POI for singles.

    Others like to change their comb setting higher for handicap than for singles.

    I have known people who are extremely successful in both camps.

    Its kind of up to you.

    If your yardage is 20, I wouldn't do a thing.

    Try it and see if you like it.
  9. timb99

    timb99 Well-Known Member

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    <i>Depends on the gun, high rib or low rib makes a difference. Unsingle or top single makes a difference. </i>

    Oh please, hmb, please, please explain why. And this time, do try to make sense.
  10. zzt

    zzt Active Member

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    timb99, it makes a difference because the shotgun recoils upwards as well as backwards. The upward recoil is a rotation of the gun about your shoulder. The more inline the barrel is with the recoil pad's contact point on your shoulder, the lesser that rotation will be. For any barrel configuration, a higher rib moves the barrel lower and more in line with your shoulder.

    A top single or the O barrel of an O/U is necessarily higher the an unsingle or the U barrel, so the rotation is greater.

    Your shotgun barrel is rising (rotating) while the shot is traversing the bore, so the greater the rotation the higher the barrel will be when the shot exits. Given the same sight picture when fired, the higher barrel will have a higher POI than a lower barrel. Hence the need to check it on the patterning board.

    BTW, HMB could also have added that stock pitch, shell speed and barrel porting also affect POI.
  11. timb99

    timb99 Well-Known Member

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    zzt,

    OK, I will accept that while those things may make a difference, I suspect they may result in changes to the POI measured in fractions of an inch at 35 to 40 yards.

    A fly on your bead might make a difference too.
  12. hmb

    hmb Active Member

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    Tinb99, The height of the sight plane above the center line of the bore is what makes a difference in the POI. When leaving the barrel the shot has to cross the sight plane, it then travels above the sight plane and then crosses it again on the way down. The higher the sight plane above the barrel the greater the upward angle of the barrel, this is what causes different POIs at a given distance with guns having different rib heights. HMB
  13. zzt

    zzt Active Member

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    HMB, at a "given" distance, a POI of 6" high is 6" high regardless of the barrel position or rib height. Everything was taken into account when you set your gun to print x high at y distance.

    The differences in POI show up at any distance shorter or longer than the "given" distance.

    timb99, you would be surprised at how much of a difference it makes.
  14. timb99

    timb99 Well-Known Member

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    hmb, while that is true, it makes absolutely no difference if you set up a gun to shoot a certain height above your POA at target distance.

    Now don't confuse the matter by talking about what yardage you "zero" the gun at. That is not what I'm talking about, because it really doesn't matter, and I really don't care what yardage a shotgun zero's at.

    I can show you with calculations that for two shotguns, one with a high rib, the other with a low rib, that IF YOU SET THEM BOTH UP TO PATTERN THE SAME HEIGHT, AT TARGET DISTANCE, the difference in trajectory of the shot, is fractions of an inch.

    I'm talking about comparing an unsingle with a 2 inch rib that patterns 10 inches high at 35 yards versus a top single with a 0.25 inch rib that patterns 10 inches high at 35 yards.

    The trajectory is almost exactly the same. And you would shoot them exactly the same. And if you didn't change ammo, there would be no difference.
  15. timb99

    timb99 Well-Known Member

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    zzt,

    <i>you would be surprised at how much of a difference it makes.</i>

    The MOST it can POSSIBLY be is the difference in the dimension between the two barrels, which is about an inch.
  16. zzt

    zzt Active Member

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    not correct timb99. You are not considering the differences in rotation I discussed above.
  17. gun fitter

    gun fitter TS Member

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    Time of flight increases with distance and so does distance traveled by the target.that along with drop can be enough to make an adjustment.

    Joe
  18. timb99

    timb99 Well-Known Member

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    How can that possibly be zzt?

    Let's say it is you, zzt, shooting the two guns. One is an unsingle, the other a top single. The difference, for the sake of argument, between the centerline of the muzzles of the two guns is an inch and a half.

    Your stance will not be much different when you are pointing the guns at the patterning board, right? No, it will be exactly the same.

    Your gun point will be almost exactly the same at the time you pull the trigger, right? The only difference being that the unsingle barrel will be about an inch and a half lower than the top single barrel. Right?

    When the shot leaves the muzzle, perhaps you get a little more rise from the top single gun than the unsingle gun, so lets say half an inch. It can't be much more than that, right? How can it?

    So now we are talking about the difference in where the two muzzles of the gun are being about two inches. Are you with me so far?

    And for the sake of argment, I am being generous in the amount of difference, because I don't believe it is that much.

    You are using exactly the same shells, so the physical trajectory from point A to point B will be identical. Right?

    So how in the blue blazes can there possibly be more than two inches of difference in the trajectory of the two shots if they both end up patterning on the pattern board at exactly the same place?

    And here's more evidence. Both shots are converging to the same POI. Right? So no matter how far apart the two shots start, the difference between the two will get smaller as the shot travels towards the pattern board.

    It's physically impossible to say that is not true.

    So by the time the shot has traveled to 20 or 25 yards, and the pattern has opened up to 15 inches or so, the difference is indistinguishable.
  19. Hap MecTweaks

    Hap MecTweaks Active Member

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    gun fitter, Joe, are you saying that a shot charge regulated to hit at 40 yards as a 50/50 deal further drops again? How can that be unless you measure drop farther out?

    If you use the centerline of the shotguns bore to AIM at an aiming point at 40 yards, yes, it will drop 3 to 4 inches! Regulated by the rib, 1/2 the barrel diameter and bead it raises that drop number to a 50/50 pattern at 40 yards. You certainly don't add in another drop of 3 to 4 inches!!

    The time of flight a shot charge in the air dictates raising the POI, not the shot drop!

    TimB99, I also agree with your thoughts.

    Hap
  20. gun fitter

    gun fitter TS Member

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    What I said is correct and was relating a 16 yrd gun to moving to 27 yrds.

    everything increases the drop and time of flight and distance the target travels all indicating a possible adjustment alowing the gun to shoot a bit higher.

    Joe
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