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Adjustable Rib Dilemma

Discussion in 'Shooting Related Threads' started by 8point, Jul 12, 2010.

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  1. 8point

    8point Member

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    I have always shot trap guns with fixed ribs and fixed combs, but now I bought a Silver Seitz with both adjustable rib and Comb. My Dilemma is I like the gun to shot 60/40 with a figure eight bead site picture. When I move the rib to shoot 60/40 and then move the comb to get the figure 8 the gun still shoots 50/50. If I move the rib to shoot 100% above point of aim and then move comb to maintain figure 8 beads it still shoots 50/50. Should I only move one and not both? Dave
     
  2. hmb

    hmb Well-Known Member

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    You have the choice of moving the muzzle end of the rib down, or moving the comb up, or both. All will make the gun shoot higher. HMB
     
  3. jimrich60

    jimrich60 Member

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    In setting up POI with an adjustable comb and rib, you should first set the comb for the desired POI. Then use the rib to "fine tune" the POI if desired. I know there are a lot of differing and conflicting instructions on this, but that is not only the guidance from Beretta, but also simply a logical method that actually works. Remember that moving a comb up raises the POI, and lowering the comb lowers the POI. The rib (at least if the pivot is at the rear) works in the opposite direction. That is, to raise the POI, lower the front of the rib/bead

    So if you are lowering the rib to raise your POI from 50/50 to 60/40, then lowering the comb to reachieve that mythical figure eight sight picture, you have just cancelled out the POI adjustment you made with the rib. The line of sight (and therefore the "sight picture" ) has to change in order to change the POI (that is, you raise the rear sight (your eye, via the comb) or lower the front sight (the bead) to raise the POI and this will mean that you will see more of the rib. The apparent bead relation will change correspondingly. You will have to stop trying to get back to the original bead view and you will be able to raise the POI

    Jim R
     
  4. KEYBEAR

    KEYBEAR Active Member

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    I can,t believe your moving the rib right . If you move the rib to the top setting in the back and the lowest in the front how high dose it shoot weith a figure 8 ??
     
  5. 7bcshooter

    7bcshooter Member

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    I am on my second gun with an adjustable rib and comb and this is what has worked for me. First pattern the shotgun with the beads in a figure 8 configuration. If you want to raise the POI, lower the front of the rib about 1/16 of an inch and raise the comb accordingly to regain the figure 8 sight picture and test fire again. Keep making small adjustments until you get the pattern where you want it. You should also be doing the test firing from a rest and not offhand. I do all my test patterning at 30 yards. If this doesn't work, you might want to shoot the gun and have a dummy round in the group of shells you are shooting and see if you are flinching. Now you have my two cents worth and that is probably about all its worth.

    Craig
     
  6. KEYBEAR

    KEYBEAR Active Member

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    Craig A Silver Seitz Adj. rib moves on both ends and has notches (thinking four) . You move both ends to adj When one goes up the other goes down
     
  7. 8point

    8point Member

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    Jim's suggestion makes a lot of sense so I'll try that method. The gun's rib is a copy of a moneymaker rib which I have instructions for. It does not mention anything about the comb though. My rib pivots in the middle and if the rear notch is in the lower most slot and the front in the upper most slot the gun shoots 50/50. If the rear is in the upper most slot and the front in the lowermost slot it shoots 100/0. The two positions in between these gives you 60/40 and 70/30. The 100% position raises the pattern 13 inches compared to point of aim. Thanks all for your advice Dave
     
  8. Ted K.

    Ted K. Member

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    Here's something I posted on this subject about two weeks ago on this forum:

    Subject: Adjusting an adjustable rib and adjustable comb
    From: Ted K.
    Fri, Jun 25, 2010 - 10:18 PM ET


    Here's my take on how to adjust the rib and comb on a gun that allows both to be moved. (I posted this earlier at the end of a long thread that I suspect no one ever read.)

    First, I have noticed that I can get the sight picture I want (for me, a figure 8) just by changing how hard I push my cheek against the stock. So initially, I'll put the comb somewhere that seems comfortable and that gives me my figure 8.

    Then I will shoot the gun (usually at no. 3 position, with the thrower set to throw straight-aways). I'll put the target just on top of the bead and see what happens. Let's say I get a clean miss. Next bird, I point the gun about 6 inches below the bird. Maybe I get a break that indicates that I'm hitting the top of the target. That suggests that the gun is shooting high. I'll try a few more shots with space between the front bead and the target to be sure. If I am convinced that the gun is shooting too high, I'll raise the muzzle end of the rib (which actually moves the barrel down).

    Now I'll try a few more shots, with the target positioned just above the bead. Maybe I'll make some more (hopefully smaller) adjustments. When I get to the point that I'm smoking the birds (or at least getting very solid center hits) with the target sitting just above the bead, I stop adjusting the rib.

    Now I'll turn to the comb, and adjust it so that I don't have to force my face anywhere. What I'm looking for is that when I mount the gun, I immediately see a perfect figure 8, without any need to "push" my face anywhere. What I want is to have the comb set up so that I automatically see the correct bead picture when I mount the gun. Every time.

    Now back to the range and shoot the gun (again just throwing straights from position 3). Maybe (but probably not) I'll make minor adjustments in rib height if I'm not getting very centered breaks. And I'll adjust the comb slightly so that the figure 8 is still there without pushing (usually not necessary).

    At this point, the gun points where I expect it to, and I see the desired bead alignment when I mount the gun.

    This system will work for any sight picture you like and any alignment with the target you prefer, i.e., you can adjust the comb so that the rear bead covers the front bead and/or adjust the rib so that the target "floats" a certain distance above the front bead when hit in the center.

    Note that this system doesn't rely on comb adjustments to change the POI - that's done by adjusting the rib. If you use the comb to adjust the POI, and then adjust the rib to get the desired sight picture, you will find that the rib adjustment has changed the POI.

    Try it - you'll like it.

    Ted K.
     
  9. Rastoff

    Rastoff Active Member

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    I'm missing something here. It is absolutely impossible to have the gun shoot 50/50 with the comb up and down. If you set the rib for 100/0 you will have to move the comb up to get a 8. Then, if you set the rib for 60/40, you will have to move the comb down to get a 8.

    The gun will not shoot the same with these two different comb positions.

    Am I missing something in your first post?
     
  10. zzt

    zzt Well-Known Member

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    Dave, Jim and some others here didn't get things right. You have what is called a tetter-totter rib, the same as on a Perazzi. You already know that if you lower the front one notch, you raise the rear one notch. That's how a tetter-totter works.

    Here are the facts. Anytime you move the bead, you change POI. Anytime you move the comb, you change POI. All adjustments are additive. If you are actually seeing a Fig 8, it is not possible to do as Jim suggests, because then your eye would be blocked by the receiver, or rear of the rib, and you would not see the bead at all.

    Here is how it works on my Perazzi, and it will work the same on your gun, except the distances may be different.

    Every time I lower the front of my rib one notch, I raise POI by approx 1.4" @ 40 yards. However, my bead alignment is different. Perazzi says that you should put 2mm of spacers under the comb for each notch you adjust the front of the rib down. That brings the beads back into a Fig-8 alignment (or whatever alignment they were in before you moved the rib). That 2mm of height changes my POI by about 2.6" at 40 yards. So the combination of lowering the bead one notch and adding 2mm of spacers under the comb raises POI by 4" @ 40 yards (1.4" + 2.6").

    So I'll say again, moving the rib changes POI and moving the comb changes POI, and the changes are additive. To make positive or negative changes in POI the bead and the comb must move in opposite directions. If the bead goes down (lowering rib in front), the comb must go up to maintain the original bead alignment, and vice versa. If you move your bead and comb in the same direction, the movements cancel each other out to some extent (or possibly all in certain rib configurations).

    I'm not hung up on a Fig-8 alignment, so I use each adjustment individually at times. I make small adjustments using only the rib, medium adjustments using the comb, and larger adjustments using both at the same time.

    Since you prefer to always see a Fig-8 alignment, you must move your rib AND the comb to maintain that when changing POI. That means you only have four discrete adjustments. If your notch spacing is equal, I'd suggest your four POIs are 0", 5", 10" and 15" high @ 40 yards, assuming your lowest front notch really is 100%.
     
  11. ivanhoe

    ivanhoe Well-Known Member

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    Everyone of those guns that I have seen or worked on all come with a manual that usually explains what to do to achieve your desired setup. Sure would be nice if people could and would read these things.

    Bob Lawless
     
  12. Neil Winston

    Neil Winston Well-Known Member

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    I gave up fiddling with them both. I set the rib to shoot low and now just move the comb. I am finally starting to hit something with the gun after two years of confusion and frustration.

    Neil
     
  13. AveragEd

    AveragEd Well-Known Member

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    Bob, I felt the same way for the 38 years I spent as an auto dealership service manager. People spend $30,000 or more - a lot more, in some cases - for a new car but won't spend a half-hour learning how to use it. But reading the manual doesn't always help with guns.

    A lot of trap gun owner's manuals tell you to move the comb or rib to get the POI you want and then move the other to get your sight picture back. That's double-adjusting and the person following those instructions will spend untold hours chasing his POI around - too high, too low, too high, too low and on and on. Back when the Browning "Plus guns" came out, I watched two state champions drive themselves goofy with their BT-99 Plus owner's manuals and wrenches.

    Moving the comb up raises POI. Moving the front of the rib down to regain the figure-8 does also raises POI. And it works the same way if you move the rib first or if you adjust one of them for a lower POI. It might work better with a teeter-tooter rib but all my adjustable guns have had rear-pivoting ribs.

    Ed
     
  14. jimrich60

    jimrich60 Member

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    zzt

    If you had actually stopped to read my comments, you would have noted that I caveated them with the comment that they applied only if the adjustable rib was rear pivoted, not if the pivot point was in the middle of the rib. In such cases (and very few adjustable ribs are pivoted in the middle) the POI adjustments may work differently (since I do not have a mid rib pivot, I cannot say from personal experience) but that was not the question, nor was it part of my response to 8point. Nonetheless, it is basic that raising the comb raises the POI and lowering the front bead also raises the POI. The bead alignment is really irrelevant in the equation, except for a personal preference or, in my opinion, a mistaken belief that somehow a "figure 8 bead alignment" is the mythical key to proper gun alignment. Except for ensuring you are not canting the gun, and that you are looking straight down the rib, the middle bead is totally unnecessary and often little more than a distraction. JMHO.

    Jim R
     
  15. ivanhoe

    ivanhoe Well-Known Member

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    Ed I don't own one anymore but here is what I found on the tip rib designed(hinged in the middle)if you tip the rib all the way down in the front you will not be able to see the beads at all(at least I couldn't)so you must double adjust to see the beads.

    I can't believe that when you can't see the beads that any move you make with the comb will change anything before you can at least see the beads. JMO

    Bob Lawless
     
  16. Setterman

    Setterman Well-Known Member

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    I've had 4 adjustable rib guns. Never had a problem finding the POI AND getting a Fig 8 bead arrangement. 7bcshooter had a great explanation.
     
  17. jimrich60

    jimrich60 Member

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    Bob:

    I don't now, and never have, owned a gun with a mid-pivot rib, but thinking about it logically, I would think it would work something like this. For instance, if you wish to raise the POI 6 inches, then what you could do is to lower the front bead such that the POI is raised 3 inches. That, of course, would also raise the rear of the rib correspondingly. Then you would raise the comb such that you raise the POI another 3 inches, for a total POI change of +6 inches. In the process you would then, in theory, be re-establishing the same "line of sight" down the rib that you had before the the double rib/comb change. In this way (and only with a mid pivot rib) you could, in theory, maintain a "figure 8" bead alignment, if that is what you saw before the change in POI.

    Jim R
     
  18. zzt

    zzt Well-Known Member

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    Jimrich60, I actually did read your comments. All adjustable ribs with adjustable combs work exactly the same way regardless of where they pivot. The only difference is with adjustable "rib" guns that actually move the barrel, not the rib, as in K-80s.

    I'm with Ivanhoe on this one. It is easy to do, but if you can't figure it out, simply read the manual.
     
  19. AveragEd

    AveragEd Well-Known Member

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    Bob, when you move the comb, you move the rear sight. Regardless of where the front sight is, that changes the gun's POI. But I'm sure you already knew that, so I must have missed what you meant.

    Ed
     
  20. zzt

    zzt Well-Known Member

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    Ivanhoe, mathematically, when you move either the bead or the comb you adjust POI. If you adjust your gun so that you cannot see the bead, your POI is going to be all over the place (LOL), because eye/receiver/bird is not as accurate as eye/bead/bird. However, I understand your point.
     
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