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changing POI w/ fixed rib and comb

Discussion in 'Shooting Related Threads' started by acss, Sep 17, 2009.

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  1. acss

    acss Well-Known Member Supporting Vendor

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    have a local shooter who purchased a BT99 32" fixed rib and fixed straight comb- he is a very good shooter - tends to hang on the target and you cud say - shoots delibrate ( aims) . without changing his lifelong technique- How do we make the gun shoot flatter??? now he is chunking rocks and taking the tops off! his comment to me was " i dont want to aim a foot(?) under the rock"!!! ps - he has been shooting an 870 trap, dont know which model?
     
  2. hmb

    hmb Well-Known Member

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    If you increase the height of the front sight this will lower the POI. If you're handy you can make an add on rib from a strip of balsa wood that you can get at a hobby store. Tapered and about 3 inches long, have it high at the muzzle end of the barrel where the front sight is located. About 3/8 of an inch higher will be about right. HMB
     
  3. zzt

    zzt Well-Known Member

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    Add an adjustable butt plate and move the pad down and/or sand some wood off the comb.
     
  4. AveragEd

    AveragEd Well-Known Member

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    Boy, that's a tough one. Making that gun shoot higher wouldn't be too difficult with moleskin on the comb but lowering the POI requires either bending the barrel (poor choice) or having the comb made adjustable in such a way that he can lower it below level with the rest of the stock. Perhaps an aftermarket rib of some kind would work.

    Of course, he could just take the time to learn to shoot what is propably a normal trap gun. Remington trap guns are known to be flat-shooters.

    Ed
     
  5. Dickgshot

    Dickgshot Well-Known Member

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    A thin add-on rib as suggested by hmb, except it doesn't need to be tapered and it doesn't need to be balsa. A tapered rib would give the same visual bead relationship but that might be unimportant. Balsa is soft, porous, and a very light color. It's also a huge pain to paint. At the hobby shop you will find plastic strips used in model railroads that are a dark gray color, about 1/8" thick and 5/16" wide. Perfect for an add-on rib. You can attach them with silicone seal or double stick tape.
     
  6. Chip Pitcairn

    Chip Pitcairn TS Member

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    Briley can make a choke tube that adjusts the point of impact at a certain distance. I don't know what it would cost. Chip
     
  7. ivanhoe

    ivanhoe Well-Known Member

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    zzt

    "or sand some wood off the comb."

    Gee sounds like an easy fix to me.

    Bob Lawless
     
  8. ExFedex

    ExFedex Active Member

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    Sounds like your friend has an RP model BT-99 like mine. I have a 3/8" balsa strip taped to the rib and its blackened with one of those large indelible markers. Easy to recoat. This allows me to use the adjustable comb to its full advantage now in changeing the point of impact. Gun now shoots where I want it to and my head is a little more upright.
     
  9. brent375hh

    brent375hh TS Member

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    I find that by simply holding a higher gun over that house keeps me from topping them, since I don't have as much upward momentum. It may sound counter intuitive, but it works for me. Of course if you wait until they are no longer rising this won't work.
     
  10. jimrich60

    jimrich60 Member

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    First, an adjustable buttplate/pad, while a nice feature for its purposes, will have no affect whatsoever on POI. POI is solely determined by the relationship of the rear sight (your eye) and the front sight (bead). That is it, although, of course, you can achieve a change in this relationship by a number of methods. An adjustable buttpad does not change this relationship, it only changes how the butt fits your shoulder. The relationship is established by how your face (and consequently eye position) fits on the comb, and where the front bead is then in relationship to your eye.

    Since, in this case, the goal is to lower the POI, the simplest way to do this is just to install a higher bead. This will lower the POI, (same as raising the front sight of a rifle or pistol) though you would need to experiment to find the right height to set POI where it is wanted. This has the advantage of making no permanent changes to the gun, since the bead could be changed back. Either have a gunsmith install a larger/higher bead, or use one of the flourescent type beads like Easy Hit or others, which tend to sit higher than a regular bead, thus lowering POI.

    The second way to lower the POI would be to "lower the comb" (again, same as lowering the rear sight of a rifle or pistol). This would require altering the comb (by sanding or filing of the comb down) or by lowering the drop through altering the stock where it bolts to the receiver. This is a gunsmith or fitters job, makes permanent change to the gun, and (unless you sand down yourself) can be expensive. Also, if you go too far, hard to replace wood.

    Thirdly, as some have suggested, you can raise the front sight by raising the entire rib, through an add on rib. By raising the rib, without raising the comb-this is important), you in effect are simply raising the front sight. How much to raise the rib would have to be determined by experiment. Here is where use of a temporary balsa rib is helpful. Cut a strip, start with about 1/8 inch height, tape on temporarily, and see if that works. If POI is still too high, make one 1/4 inch and try. Once you have acheived a proper POI this way, you can have a proper add on rib made for the gun (various makers do this) to meet your needs. Again, though, this is not cheap. And if raising the rib to lower the POI, again I emphasize, you do not raise the the comb. Converserely, if you wanted to simply raise the rib (for other reasons than POI), you would have to raise the comb the same amount as added rib to maintain the POI.

    Given what is wanted here, I would simply add a higher bead. It is quick, easy, inexpensive, and easily changed back if/when wanted.

    I would say that a BT99 thats "shoots too high" is, in my experience, somewhat unusual. Most users I have known, as well as myself (and I have owned/shot several, both adjustable and non-adjustable) find the BT99s tend to shoot low, at best 60/40 and more often for many about 50/50. But it may be simply how the shooter holds/cheeks the gun. It may also be that the shooter in this case is one of those (possibly as a result of wing shooting habits) either consciously or subconsciously, uses the barrel rather than the bead to "cover" the target. It might be better to learn to hold under the target in order to better see and concentrate on the target, rather than the bead/barrel. This latter will inevitably result in more lost targets, especially hard rights/lefts which are difficult to follow if "covering the target" rather than keeping the target clearly in your vision slightly above the bead (of course, you should not consciously "see" the bead or barrel, only the target and concentrate on that. But, many "wing shooters" have some difficulty doing this and it does take some work to overcome the tendency.

    Jim R
     
  11. KENENT1

    KENENT1 Active Member

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    raise the front bead, in fact unscrew it about 2 turns, if it is a 56 pitch thread that would raise it around .036, this would be about 6 inches, give or take @ 30 yards.

    if this works either get a taller bead, or locktight the original at the height you want.



    tony
     
  12. JACK

    JACK Well-Known Member Supporting Vendor

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    unless he has done this, he is just yappin


    [​IMG]


    another indicator of whare I shoot my MX3.


    [​IMG]


    This is my standard way of testin POI. The 13 yard Winston method. This gun is shooting 75/25 plus. Withe space between the beads.
     
  13. Paladin

    Paladin Well-Known Member

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    Brownells has extended front beads. Have a gunsmith install one correctly. I used one on a fixed rib Beretta for 4 years.
     
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