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Top Barrel shoots lower than bottom barrel?

Discussion in 'Uncategorized Threads' started by truthseeker, Mar 8, 2008.

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  1. truthseeker

    truthseeker Member

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    I have a Perazzi MT6 and I patterned it today. Well at 22 yards the bottom barrel shoots about 80 percent high and 20 Percent below where I am aiming and the top barrel shoots 10 percent high and 90 percent low of where I am aiming. What the hell is going on here? Shouldnt the top barrel shoot a little higher than the bottom barrel? How can i get the top barrel to shoot the same as the bottom barrel? Thanks!

    I added these pictures to show you what i am talking about:

    This is what it is supposed to look like


    [​IMG]


    This is what mine looks like


    [​IMG]



    [​IMG]



    [​IMG]
     
  2. kirbythegunsmith

    kirbythegunsmith Member

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    This may not be exactly pertinent for your specific example here, but will be of use for a wide range of shooter's situations.

    --------


    I have been trying to describe the problems with choke tube installations not being in line with the bore for about 23 years.

    I had noticed non-choketube barrels shooting off before then, but when I had a rude example come in the shop that hit 11" high at 19 yards, that proved to me that choke tubes were not a factory miracle.

    Some time later I saw a $7000 trap O/U with crooked choke holes right from the factory, and back then that money would have bought a new mid-sized car.

    I wish I had an answer for every lousy hitting barrel (that people wanted to hear), but usually the best approach for a crooked choke tube hole starts with a hacksaw and finishes with a new (and precise) choke hole. Just about anything else is just amelioration, not remediation. (Sorry for the $2 words, but they fit the description best: you don't need a band-aid, you need an amputation)

    See some of my articles at the website to notice some real disastrous installs and a barrel about to explode (if fired one more shot) in article 3.



    Kirby
     
  3. BIGDON

    BIGDON Well-Known Member

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    Maybe because it is set up for doubles. High rising 1st bird and flater 2nd bird.

    Don
     
  4. hmb

    hmb Well-Known Member

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    A slow doubles shooter. HMB
     
  5. K80433SC

    K80433SC Member

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    Truthseeker : Let's forget about choke tubes for a second.

    Your original question was : "Shouldn't the top barrel shoot a little higher than the bottom barrel" ? I believe a "What the hell is going on here" ? was thrown in for good measure.................*smiles*

    The nature of the beast suggests that the bottom barrel WILL SHOOT HIGHER than the top barrel in nearly every O/U that you find. While this may be contrary to "logic" or what might be determined by visual appearances, it is -- as they say......."the way it is".

    In your case, I have no experience with the Perazzi MT6. I would be at an admitted loss to offer anything that might help you in your quandary. Just keep in mind that (in an un-altered version of the barrels), your top barrel will shoot lower and the bottom barrel will shoot higher.
     
  6. BIGDON

    BIGDON Well-Known Member

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    hmb: You must be faster than the speed of light because every one I know the 2nd bird is starting to flatten out with the exception of a select few.

    Don
     
  7. Ljutic111

    Ljutic111 TS Member

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    It would be nice if both barrels pattern the same but unfortunately most don`t and the shooter doesn`t even notice this and is wondering why they only use the upper or lower barrel because they shoot better with that particular one ?? With my X SKB , I had to aim 12 inches lower on the target with the lower barrel than the upper ?? Got rid of that loser fast .
     
  8. zzt

    zzt Well-Known Member

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    truthseeker, you definitely have a problem, but we don't really have enough information to help.

    Try your POI testing again. Do it from 20 or 22 yards, but from a rest. Shoot at least 5 shots from each barrel, using a new sheet of paper each time. Then determine the pattern center an measure where it falls in relation to the point you aimed at. Presumably there are different chokes in each of your barrels, so you cannot use % over, % under to determine anything.

    You will then have a set of numbers that is unambiguous. Such as Under barrels shoots 4" high at 22 yards, and Over barrels shoots 1" low at 40 yards.

    This will do two things. First it will tell you what you are actually dealing with. Second, it will tell a competent gun/barrel smith what can be done to remedy.

    We also need to know if you barrels are fixed choke or choke tubes. If choke tubes, you have a lot more checking to do.
     
  9. GunDr

    GunDr Well-Known Member

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    Using the term "percentage" only works for patterning at 40yds. This was/is the standard that's been used for eons. Also the 20-22yd test will not tell you exactly what your gun is doing, unless the only pupose for the gun is for skeet shooting, then it should be done at 25 yds.

    Re-pattern the gun at 13 yds from a rest (Neil Winston's method). POI at this 13 yds should duplicate itself at 40 yds. The 13 yd test allows an easier "aim" for most shooters and a little less walking.

    If you feel you can shoot your gun...from a secure rest...then shoot it at 40yds.

    Determining the POI of the gun, do not look at where the outside edge of the pattern lies in relationship to the "aiming point", but take a measurement from the center of the pattern to the center of the aiming point/hold point.

    Trying to determine a percentage at any other yardage, when comparing two different bbl's with two different chokes, ie..mod and a full, the mod will always appear to be shooting lower, because of the larger pattern, and more pellet holes below the hold point, even though the center of each pattern is equal.

    With regards to the bottom shooting higher than the top....you will like it that way....ask any AA shooter. A bbl with a little more "built-in elevation" works nice on that faster rising first target.
     
  10. BDodd

    BDodd TS Member

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    Sir truth, I've not gone through the other responsees but will answer your original and basic question. The norm for guns set up for doubles is to have the lower barrel shoot higher than the upper barrel so that you can take the first bird that is rapidly rising with the high shooting tube and then take the second bird which is no longer rising so fast with a "flatter" shooting tube. The mantra for a doubles O/U is open choke and shooting high in the lower barrel and tight choke and flatter POI for the upper. And, I'll wager most Perazzi tournament O/Us are likely to be close to that setup.....Breakemall....Bob Dodd
     
  11. tcr1146

    tcr1146 Well-Known Member

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    Bob Dodd:
    I agree 100 % with you, but, if he has done his patterning accurately, you will notice this his top barrel is shooting well below his aimpoint! This is not good at all! His top barrel is not even 50 %! That gun is in trouble for any form of trapshooting! Tom Rhoads
     
  12. Jawhawker

    Jawhawker TS Member

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    truthseeker, first as others have stated, shoot several sheets of paper from a rest for each barrel. Neil and others now advocate 13 yds. I do mine at 20 yds. Then see if your results are the same. If so and since this is a tubed gun, try different tubes in the top barrel. It may be this simple to change as I've seen similar scenarios where choke tubes were involved. If its truly the barrel, then you could have a special tube developed to raise POI somewhat but at best its still is going to be a "flat shooter". If it was me I would trade for another gun with this extreme to contend with.

    GunDr, I personally like both barrels shooting the same POI or very close to it and several of the "AA shooter" friends like it that way.
     
  13. BDodd

    BDodd TS Member

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    A-HAA, that's what I get for speed reading Tom. Mea Culpa - Maybe the last owner shot 2nd birds 10' off the ground, eh?...Bob Dodd
     
  14. BIGDON

    BIGDON Well-Known Member

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    DA: I get out a fair bit and would venture as others have stated higher lower for 1st and flatter top for 2nd is more of the majority. Most doubles guns I have owned and have seen are set up that way. To each his own.

    Don
     
  15. miketmx

    miketmx Well-Known Member

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    I had a DB81 that had a POI problem very similar to your set-up. The bottom barrel shot just right but the top barrel shot way low and I couldn't hit a 2nd bird with it. I got rid of that gun and bought a Browning Citori and both barrels shot to the same place, I now have a Perazzi MX3 and both barrels shoot to the same POI. A good friend has an MT6 combo and the O/U shoots just fine for Doubles but he does not use the Unsingle barrel because you guessed it, it shoots too low. This is not what you want to hear.
     
  16. hmb

    hmb Well-Known Member

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    Don,

    That is a very astute observation on your part. I developed a system for shooting doubles fast. I'm righthanded and shoot the first bird using my left eye, this allows me to see the first bird while it is still under the gun, and I shoot the first bird while it is still under the gun. This is accomplshed with no gun movement. As soon as the shot is fired I move to the second bird and shoot it using my right (dominant) eye. The speed at which I shoot the second bird is fine tuned to the guns top barrel POI. HMB
     
  17. Jawhawker

    Jawhawker TS Member

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    truthseeker, I don't think your going to find a solution to your problem... I would look for a different gun.
     
  18. 1st worker

    1st worker TS Member

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    Big Don I have shot doubles with HMB and he is the fastest doubles shooter I have ever seen. If he shot any sooner he would hit the houseand the second bird is still rising when he gets to it.
     
  19. miketmx

    miketmx Well-Known Member

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    Very interesting barrel hanger to say the least! Have you tried pattern testing the top barrel with the screws fully tightened and then fully loosened to see what effect that makes?? Do you know how to bore sight and a read a Barrel. Insert a deprimed 12 ga empty hull in the breech and a deprimed 20 ga empty hull in the muzzle and look through the breech end at a light source. If the barrel shows perfectly concentric rings then your barrel is "true" ie. not bent. Put the deprimed 12 ga empties in both chambers and rest the barrel set on a picnic table in your back yard and look through the bore at a distant bullseye on the back fence then raise your head without moving the barrel set and note the sight picture down the rib at your target. This trick will give you some valuable information without actually shooting the gun. Let us know the results.
     
  20. Neil Winston

    Neil Winston Well-Known Member

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    ...and if you try MikeTMX's method, but sure you take the de-primed shell out of the muzzle before you shoot it! This is voice of expensive experience.

    I've never seen anything like that either. PPB, what was it for?

    Neil
     
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