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Choke tube problem

Discussion in 'Shooting Related Threads' started by Steinkruger, May 21, 2010.

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  1. Steinkruger

    Steinkruger TS Member

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    i was taking out my choke tubes tonight to clean them and there was one that was split down the middle. what would be the cause of this??

    Doug Steinkruger
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    I don't understand, Doug. How could it be split anywhere else than "down the middle?"

    Neil
     
  3. Steinkruger

    Steinkruger TS Member

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    i meant the wall of the tube is split on one side running the whole length of the tube. I hope this helped.
    Doug
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    It seems to me it had to have been installed in a threaded hole the unthreaded part must have been too big for. Do you have any other tubes with the gun? If so, it might be interesting to mike the outside diameter of the choketube and compare it to the diameter of the hole it is intended to fit into. Or, if the tube is threaded at the breech end, just put the tube in the hole the "wrong way" and see if you can tip it at all.It should be practically a slip fit, tiny or no rocking possible at all.

    Neil
     
  5. kirbythegunsmith

    kirbythegunsmith Member

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    There are a multitude of reasons that can cause a tube to split, and one of the least likely reasons is the play between the tube and hole, since virtually all of the factory installed tubes (and many alternate installations are no better for fit) have substantial slop between the tube and hole. I don't appreciate their lack of fit; I just note the existence and state that typical and factory tubes do not have any meaningful backup support from the barrel to resist expansion forces, and there are generally sloppy tolerances all around that are quite the opposite of a custom fitted choke tube.

    The 2 most common reasons I see for a tube splitting are either material defect (includes excess hardness/brittleness for the usage) or pounding by hard shot, like steel shot, and usually it is a combined effect of pounding and material brittleness.

    You didn't mention what brand of tube was split, so if you don't want to post, email me and please include a picture.

    Here is one example that I will show of just such an occurrence. After those 2 pictures of that example, see the example after of an expanded/pounded choke that moved so far that the barrel shows an exterior ring. Those reactions are more common (tube expansion) in my experience than splitting. The real monkey wrench is bore obstruction bulging/splitting/bursting examples. You wanted to see some examples of that, too? How about that last picture posted? Any input of why you think that occurred?

    This is the sort of thing I encounter by being a choke and barrel specialist.

    Kirby

    <a href="http://s186.photobucket.com/albums/x109/kirbythegunsmith/?action=view&current=chokecrack-2.jpg" target="_blank">[​IMG]</a>

    <a href="http://s186.photobucket.com/albums/x109/kirbythegunsmith/?action=view&current=chokecrack-1.jpg" target="_blank">[​IMG]</a>

    A more typical reaction from excess pounding action of large steel shot or other hard pellets.

    <a href="http://s186.photobucket.com/albums/x109/kirbythegunsmith/shotgun/?action=view&current=choke-5aJPGz.jpg" target="_blank">[​IMG]</a>

    <a href="http://s186.photobucket.com/albums/x109/kirbythegunsmith/shotgun/?action=view&current=six.jpg" target="_blank">[​IMG]</a>


    Not all splitting is linear, after all. Can you guess why this happened?

    <a href="http://s186.photobucket.com/albums/x109/kirbythegunsmith/shotgun/?action=view&current=chokeskirtdamageJPG2.jpg" target="_blank">[​IMG]</a>
     
  6. phirel

    phirel TS Member

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    Kirby- Thanks for an interesting post. Your "two most common" causes of choke tube failure (material defects-pounding of the tube by heavy loads) might actually be combined into a single cause of failure.

    As the shot travels down the barrel, the barrel expands slightly and then contracts. The thin walled tube must also expand and contract with each shot. Heavy loads cause more expansion and contraction than light loads. If the wrong type of steel is used to make the choke tube, or if the correct type of steel is used but there is a defect in the section of steel used (a steel tube or bar is often not uniform throughout its length) a failure can occur.

    Neil- In your first post you asked how could a tube split anywhere other than down the middle? I contend that it is impossible for a tube to split "down the middle". The middle of a tube (central axis) is empty space. Tubes can only split along there edges.

    Pat Ireland
     
  7. Neil Winston

    Neil Winston Well-Known Member

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    Thanks for the information, Kirby. In the black & white photo, there's an over & under with a bulged bottom tube and I'll tell you one way to duplicate that. It's a three step process.

    1) You buy a brand new Perazzi Mirage from Frenchy Frigon. At home in the shop, getting ready to shoot it for the first time, you play around with sighting it in with a pair of Jack Seehase's "peeps" which disclose bent barrels and do a pretty good job, in conjunction with a good rest, of predicting where the shot will go.

    2. You take it to the range, to the pattern board, to see, at 13 yards, how and where it shoots.

    3. You notice with the first shot that the pattern is more open than expected and there are _two_ wad holes. You will never find that front peep you left in the bore, but you do have a souvenir barrel just like the one you pictured.

    Don't ask me how I know.

    Neil
     
  8. phirel

    phirel TS Member

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    Neil- To be certain, I thought about duplicating your experiment. But, Frenchy Frigon died so I cannot buy a new Perazzi Mirage from him, so I guess I will just have to accept your conclusion without verification.

    Pat Ireland
     
  9. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Careless machining of both barrel and tube may cause the fit between the tube seat and barrel shoulder allowing a gas leak. If I find tubes that don't seal at the bottom junction, I throw them away. Look for powder residue on the outside of the tube. I get a tad nervous having high pressure gas leaks in front of my eyes.

    Good post Kirby, lots of good information you shared, thanks.

    Hap
     
  10. Stuart

    Stuart Member

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    Doug, One of two reasons for that tube to do what it did. One it was made out of tubing, not bar stock. All tubing even seamless has a seam and it failed.
    Number two was it was made out of bar stock and it got too cold in the rolling process. It could still have been red hot in the roll and that's too cold. Only way to detect this is to x-ray each bar or magna-flux each piece. Even then some will pass inspection.
    Any tube manufacture has had this problem. It is hoped that we find it during manufacture.Generally you will not have any barrel damage, but check the threads anyway.
    Stu
     
  11. Dave P

    Dave P TS Supporters TS Supporters

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    Is there a single brand or so of gun or tube that stands out for this kind of problem?
     
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