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POI adjustment Question

Discussion in 'Shooting Related Threads' started by DecalDude, Sep 29, 2010.

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  1. DecalDude

    DecalDude Active Member

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    I recently purchased a Joel Etchens unsingle combo slightly used, I shot it fairly well the way it came 23s and 24s. I had a real bad night at league and got a 14 at 16s and 10 on caps.

    I went to check the gun for poi just to see if it were me or the gun. I shot all my papers at 30yrds and the first was roughly 20% above 80% below the center. I shot another the same way, same results.

    Now the gun has adjustable rib and adjustable comb. I chose to drop the rib and bring the pattern up and shot another 2 and they were 50/50. I again adjusted the rib some and got it 80/ 20. I then when out and ran 25.

    Now after seeing the papers and listening to what I did 1 of the old timer yelled at me telling me to leave the rib alone and move the comb.


    WHICH way is proper?



    Jerry Lewis
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    If you are saying that you moved the rib to change the POI at 30 yards from five inches low to five inches high I have to ask what kind of gun it is.

    Neil
     
  3. DecalDude

    DecalDude Active Member

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    Joel Etchens 687 trap combo unsingle adjustable rib. The rib was raised quite high when I got it.


    Jerry
     
  4. acss

    acss Well-Known Member Supporting Vendor

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    i really doubt if you have the rib all the way "up"- wud put the POI at -5"(?)--i didnt think theyd go below 60%--- now , personally, you shud shoot at 13 yds w/a full choke--you'll see alot more!---what were you shooting prior to the unsingle?
     
  5. jimrich60

    jimrich60 Member

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    To actually respond to your question, the usual method is to adjust your POI by first raising (or lowering if needed) the comb. The proper way to do this would be to set the adjustable rib to the middle or "neutral" position, andraise the comb to the point you are getting the POI you want. Then (since comb adjustments are normally around 3 inches per spacer, per the Beretta info supplied with my JEG Hybrid), you can fine tune the POI with the rib, moving it up or down as needed to refine the POI (the rib, per Beretta, will give a 1 inch change in POI per mark (up or down). Nothing really wrong with using the rib only as you did, of course, but using the comb first then the rib gives you a bit more latitude in adjustments. You can verify what POI you have and what you change to at the pattern board, usually recommended shoot at 13 yards in order to get the best idea of the actual POI. But in reality, the best way to adjust is to lock the trap for straight aways, then shoot from Station 3 and watch your breaks. If the largest piece(s) go upwards, then you are hitting a bit low. If downward, then you are hitting a bit high. Fine tune the adjustments until you get nice even breaks. Good luck with it. BTW, one good round or one bad round (or even days)is not a reason to start changing things.

    Jim R
     
  6. hmb

    hmb Well-Known Member

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    You adjusted the rib and then ran a 25. Sounds like you did the right thing. HMB
     
  7. phirel

    phirel TS Member

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    Jerry- For a time you stated that you shot the gun well and then things went bad. You made some sort of adjustment and started shooting well again.

    You may have experienced the "Ireland Phenomena". Last year at the Southern Grand I shot poorly on my first 100 singles in a 200 bird event. I promptly raised my comb about 1/32 of an inch and then ran the second 100. I was certain that all I needed was a little adjustment. Of course, the needed little adjustment was in me, not the comb.

    Pat Ireland
     
  8. Jawhawker

    Jawhawker TS Member

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    Jerry, an adjustable gun such as yours needs first adjusted via rib and then tweeked by comb.

    One of the largest negative factors in shooter development is the gun club know_it_all!

    If from here forth over the next few weeks your scoring remains consistent then the question that started this thread was answered.
     
  9. acss

    acss Well-Known Member Supporting Vendor

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    pat-- i wonder how many times i've did that adjustment , when "yes" it was in my mind!!!----i think the saying is-" change what you can except yourself"
     
  10. hmb

    hmb Well-Known Member

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    I don't agree with pheasantmaster. I think the comb should be adjusted first, so your head is straight and level, and your POI is as good as you can get it. Then adjust the rib so you get the desired sight picture and fine tune the POI. HMB
     
  11. DENNISMASTROLIA1

    DENNISMASTROLIA1 Active Member

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    Jim Rich60 hit it correctly--In my opinion
     
  12. dverna

    dverna Active Member

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    Mr. Ireland,

    You shoot a K-80. I assume you adjusted the comb either because you were out of rib (actually barrel) adjustment, or you wanted to change the front/mid bead relationship. But your analysis is correct; 1/32" is of greater mental than actual benefit - at least for 98% of us.

    One of the things I like about the K-80 design is that one can adjust the comb to give the head position and bead picture desired; and get the POI by bending the barrel. This is so much easier for my little pea brain to understand than altering the slope of the rib and figuring out where to set the comb and then adjusting the butt plate to get ones' head positioned. (Or do you set the butt plate and then the comb? See I am confused already!)

    Jerry, see if you can get a manual from Beretta. It is hard to believe the gun could shoot 20/80 unless something is amiss.

    Don Verna (too easily confused)
     
  13. Trap2

    Trap2 Well-Known Member

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    Twinbirds..... I believe you have it backwards. Adjust your gun to the 16yd line, record the setting, then leave it there. This allows for minute adjustments in the comb, and POI, by adding spacers, as you move back in yardage to allow the gun to shoot higher. I feel that, in order to shoot good handicap scores, you must maintain the same sight picture from both the 16 yard line and the 27 yard line. Your method demands you to learn 2 different sight pictures and requires you to shoot 2 different POI's...... Much more difficult to achieve consistantly... Just my take on it..... Dan Thome (Trap2)
     
  14. DTrykow

    DTrykow Active Member

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    So I guess I did it backwards. I'm a Left-handed Polish dyslexic shooter so I'm used to that. I started off with the comb then maxed out the rib adjustment then went back a raised the comb somemore. So I need to keep raising the comb so I'm shooting above the bird then bring the rib up to fine tune. Makes sense to me. Thanks, Dave T.
     
  15. AveragEd

    AveragEd Well-Known Member

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    My suggestion is to start completely over because as the gun is set now, it's breaking targets for you but the results won't be nearly as pretty when you use the O/U barrels. Remember, that barrel set does not have an adjustable rib, so you and the gun are going to shoot to a different POI with it.

    Pattern the gun with the unsingle and then put the O/U barrel set on the gun. Shoot at paper and adjust the comb until the gun is shooting to the same POI as you and it do with the unsingle. Then shoot the gun with that barrel set for a month or so - at least until you are certain that no further POI tweaking is needed for 16-yard shooting. Now, make spacers for the comb out of aluminium tubing, PVC pipe or any other tubular material and shoot the gun at paper to establish what the "right" POI looks like. The photo below shows my Etchen 687's stock with spacers made from PVC pipe that were painted metallic black.


    [​IMG]


    At this point, you're ready to put the unsingle on it and shoot at paper, adjusting the rib until it shoots to the same POI as the O/U. If any fine-tuning of that barrel's POI is found to be necessary, use the rib, not the comb.

    Then and only then will both barrels be able to share the same comb setting for singles and doubles. This brings me to the reason for the tubular spacers. As we age, memory fades and you WILL forget if your comb is set for singles or handicap. If you have to add a thin spacer to each comb post for handicap, it will be easy to make that determination.

    That's all the "adjusting" you'll have to do unless something about your build or mechanics changes.

    Ed
     
  16. Trap2

    Trap2 Well-Known Member

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    Twinbirds..... Tell that to Phil Kiner..... I think I'll stick with his method as he helped me a ton when I "hit the wall" at the 25. Now comfortably back on the 27, thanks to Phil's advice... Dan Thome (Trap2)
     
  17. blade819

    blade819 Well-Known Member

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    Please someone tell me how the adjustment of the comb will have a bearing on POI which is really determined by space between the barrel end bead as it relates to the center of the barrel? I believe that POI is adjusted by the rib and sight picture is adjusted by the comb. The important thing to remember is once POI is adjusted, you must have the same sight picture on every mount. Am I wrong?

    blade819
     
  18. BigM-Perazzi

    BigM-Perazzi Well-Known Member

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    Blade, because it is commonly accepted the dominate eye is the equal to the rear sight on a rifle. If you raise the eye (rear sight) relative to the front sight, you shoot higher. Best example is: how do you shoot higher with a non-adjustable rib? Raise the comb.

    Jim
     
  19. hmb

    hmb Well-Known Member

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    You can change the POI by changing the height of the front sight or by changing the height of the comb (which in turn changes the height of your aiming eye). HMB
     
  20. jimrich60

    jimrich60 Member

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    Blade

    The POI is determined by the angle between the rear sight (your eye) and the front sight (front bead). In this regard, it is very similar to adjusting the sights of a rifle. Thus raising the comb will raise the POI since it raises the rear sight (your eye) in relation to the front bead. The middle bead is absolutely of no consequence in setting the POI. In fact, the only real reason for the existence of the middle bead is to help prevent canting of the gun when you shoulder it. The desire of some for some mythical required "figure 8" bead alignment is just that a myth. It simply does not matter how much rib you see (or do not see) as you raise the comb. In fact, as the comb goes up, you will see more and more rib, the "space" between the beads will seem to increase, This can be totally ignored (and in my opinion, should be). You can achieve the same results, of course, by lowering the front of the rib (if adjustable) since you are (again, like a rifle) lowering the front sight (bead), and thus raising the POI. The reason for using the comb first and formost, is like AveragEd says, you want to set the stock/comb for whatever barrel combination you use, and then use the unsingle adjustable rib to "fine tune" that barrel to the same POI you got with the o/u barrels. Also, the comb changes will have more impact on the POI than rib changes. There are some differences in those guns which have a middle rib pivot point, but in general few guns have this, so as long as the pivot point is at the rear, all the above applies.

    Jim R
     
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