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Overbored entry on choke tubes

Discussion in 'Shooting Related Threads' started by wlc, May 7, 2012.

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  1. wlc

    wlc Member

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    Does the over size entry diameter on a choke tube affect the pattern? I guess I'm wondering if a fixed choke with a barrel of .740 and a choke diameter of .710 will perform differently than a .740 bore with an extended choke tube with a .750 entry area and reduced back to .710. Anybody know?
     
  2. john g.

    john g. TS Supporters TS Supporters

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    wic

    This is my own opinion from testing Browning Bt99s many years ago.I had a BT99 two barreled set I/M & F and a BT99 with Invectors. Not invector plus. The invector gun always had a patern with holes in it and not as even as the fixed choked gun or as tight. This was very consistant no matter what load I put in them.The pattern was more dense out of the fixed choke.

    The design is almost like a old jug choke.

    With that said I will take a fixed choke gun in the games most of the time.But I have shot some good scores with guns that have the longer choke tubes.I am shure you will get some other input on this,most very good knowlege.

    John G.
     
  3. Unknown1

    Unknown1 Well-Known Member

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    The wad and shot won't notice any difference!

    Keller
     
  4. miketmx

    miketmx Well-Known Member

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    Browning rates their screw in choke tubes in a completely different way than their fixed chokes. The fixed chokes are much tighter. For the OP question the result constriction from the bore is what matters, but never accept a choke job where the entry to the choke would cause the wad to catch and ruin the barrel.
     
  5. Steve W

    Steve W Well-Known Member

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    I certainly can't tell the difference, but a very, very famous barrel smith told me, fixed choke barrel "almost" always outperform choke tubes in pattern density. That's why he must work on the barrel if customers want him to instal his choke tubes.
     
  6. chipking

    chipking TS Member

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    How far does the shot column have to travel (with pressure behind it)before it assumes the new diameter of the barrel. My personal belief is that with pressure pushing and inertia holding it back it will expand to fill the over size bore. If that happens just before it enters the choke then the effective constriction will be from the largest diameter of the overbore to the smallest diameter of the choke. Most choke tubes have such a short lead that for all intents and purposes it is a ripple in the shot column before the return to bore diameter (choke taper) however others have a larger than original bore lead that is longer than the entire shot column before it returns to bore diameter (choke taper) and that is a overbored barrel right before the choke. "JUG" chokes were developed as a means to provide tighter than cylinder choke patterns from cylinder muzzle loader barrels and they worked by putting a overbored section longer than the shot column just before the exit (sound familiar)(when done by folks who knew what they were doing they worked very well). That has not changed and applies to fixed chokes and choke tubes as well. When made by someone who knows what they are doing they all work quite well. When done by some nimrod who does not have a clue results will probably be less than stellar.

    --- Chip King ---
     
  7. wlc

    wlc Member

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    Thanks all, It seems logical to me that what Chip says is correct. Some tubes seem to have quite a long oversize diameter. I don't have any way of testing this and hoped that someone had. It doesn't matter anyway, I was just curious.
     
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