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How did you set up your new adjustable rib combo?

Discussion in 'Shooting Related Threads' started by bjk1972, Mar 24, 2013.

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  1. bjk1972

    bjk1972 Member

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    Id like to know the preferred way to set up a new to me combo with adjustable ribs on both unsingle and over and under barrels. Do you start at the patterning board with the top barrel of the over and under and set for your sight picture and POI or start by shooting straight aways with trapped locked on post three, making POI adjustments until desried smokeballs are had? Guess I'd like some input from shooters that have gone though the initial set up phase of an adjustable ribbed combo gun. Any input is appreciated.
     
  2. AveragEd

    AveragEd Well-Known Member

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    I get one barrel shooting where I want it with rib and comb adjustments and then adjust the other's rib until the POI matches the first barrel.

    Ed
     
  3. Avaldes

    Avaldes Well-Known Member

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    If you have an existing gun that shoots where you like, then go to the pattern board and set the new gun up to shoot to the same place. Play with the rib and comb to make yourself happy. It really ain't rocket science.
     
  4. zzt

    zzt Well-Known Member

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    bjk, unfortunately it can be a little more complicated than that, especially if the rib height of your new combo is significantly different than your old gun. I've posted several times on my procedure for checking barrel regulation, choke tube POI, etc. Search if you are interested.

    You don't say what your combo is, so start with your single barrel. I draw vertical lines on a 36" x 36" piece of rosin paper, stand 15 yards away, trace a line with the front bead and fire. I do this several times. If the centers of the shots are on the line, good. If not, I adjust my comb right or left until they are. If all your barrels are regulated well, shots from either of the O/U barrels should also be centered on the line.

    To set vertical POI I use the same process, except with horizontal lines. Using my unsingle I set vertical POI to 3.5" high at 15 yards. I use 15 yards for a very specific reason. Anything between 13 and 16 will do, as long as you are consistent. If your new rib height is much higher than your old gun, you'll want to set vertical POI to about 2.5", or a proportional amount.

    Now comes the O/U barrels. Chances are they are shorter than your single barrel, perhaps a lot shorter. That is a complication. If your barrels are all well regulated and your chokes are true, you would think that was the end of it. It isn't. If your O/U barrels are shorter than your single barrel, they will always shoot to a higher POI than the single with the same stock settings. The reason is length. So you have to set the adjustable rib of the O/U barrels to a "flatter" position to get the same POI, assuming you want all your barrels to shoot to the same place, as I do.

    My Perazzi combo is 35/34 so there is not a lot of difference. One notch higher on the front of the O/U rib does the trick. It actually shoots a tad flatter, but that's fine with me. If you have a 34/31.5 combo, you'll need two notches. If 34/30 it will be closer to 3. This is on a Perazzi, but you get the idea.

    BTW, this is the reason it is better to have a tetter-totter rib, or one that hinges in the rear, rather than one that hinges in the front.
     
  5. bjk1972

    bjk1972 Member

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    I really appreciate the input guys.I know its kinda of a dumb question, but I have never had a combo with all the bells and whistles and adjustable stuff. I have been a set it and forget it 90T type mind set up until now. ZZT, I plan on setting up as you suggest and go from there.I appreciate you taking the time to respond.Happy Easter All.
     
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