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eccentric choke tubes

Discussion in 'Shooting Related Threads' started by KENENT1, Jan 1, 2009.

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  1. KENENT1

    KENENT1 Active Member

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    A while back I had Briley make a couple of choke tubes to change my poi 5 inches to the right.......well now they seem to screw in 1/4 turn too far and throw the pattern up instead of to the right.

    I could take some material off the bottom end so they screw in 3/4 of a turn more to get the offset back to where it needs to be.

    The only other option would be to make a shim to fit under the tube to back it out 1/4 turn....I don't think this would be a good idea, I would be worried that it could become an obstruction in the barrel because it would be quite thin.

    these are Beretta Optmi tubes.


    any ideas????

    tony
     
  2. hmb

    hmb Well-Known Member

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    I like the idea of taking a little metal off the bottom, but you have to be carefull so that the choke tube flare at the bottom of the tube still has clearence relative to the bore diameter of the barrel. If it doesn't you could blow the choke out of the gun with the first shot and damage the barrel. HMB
     
  3. Gregg535

    Gregg535 Member

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    You need to keep the larger over-bore sized diameter "entrance skirt" area on the bottom of the choke tube to insure that there is plenty of clearance for the shot charge --- removing material from the bottom of the tube would be taking it from this skirt area and would not be good idea at all (it can be a major safety issue as the tube could shoot right out of the gun and rip the barrel end).
     
  4. KENENT1

    KENENT1 Active Member

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    I can rechamfer the lead in on the choke tubes.

    these tubes are quite thin walled, and long.

    tony
     
  5. country gentleman

    country gentleman Member

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    Ken,
    Although I am no barrel expert, the fitting business affords me hundreds of pattern tests each year. Ive seen many guns, perfectly fitted, that simply do not pattern well because of several reasons.
    1. Bad chokes..Improperly manufactured.
    2. Choke, load, speed combination does not function well as a whole.
    3. Good chokes with poor barrel threading.... choke not centered in the bore.
    Eccentric chokes are a fair remedy when properly built, but fair at best.
    I say only fair for this reason.

    There are 2 speed bumps in your barrel. The forcing cone and the choke. Your shot column hits those 2 speed bumps at 800mph. In a perfect barrel, its still one heck of a collision. Now consider a choke collision that alters the direction of flight while choking your shot down .030 simultaneously. POI may corrected but the patterns usually are not as good as they otherwise could have been, had the chokes been correct.

    I would never add a shim or anything else inside my barrel to try to save or remedy a silly choke tube. Before I did that I would throw the choke and the barrel off the nearest bridge and start over.
    Im sure there will be several posters that follow that have had good results with eccentric choke remedies. It is an option, just one that I personally am not satisfied with for my own competition gun.
    Good luck. Good Shooting and Happy New Year. Todd Nelson
     
  6. K-GUNS

    K-GUNS Member

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    A phone call to Briley and get their 2 cents worth before you do anything...
     
  7. KENENT1

    KENENT1 Active Member

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    Todd, I argee with you 100%....Beretta is replacing this barrel, the tubes are a tempary fix to keep shooting, there is a 4 month lead time for a new barrel, the way warrenty work goes, this could easily turn into 6 to 8 months.

    I can't figure out why the tubes are out of index... maybe I tightened them too tight and they seat further in the barrel, or there was a burr when they made the tubes, that came out, I had 2 tubes made and they both go 1/4 turn too far, strange.

    tony
     
  8. KENENT1

    KENENT1 Active Member

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    Crab...good idea!


    tony
     
  9. phirel

    phirel TS Member

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    tony- I have two ideas. The best one is to call Briley. The second one is to study the choke and figure out what happened to allow the choke to screw in differently. Screws do not normally change like that. Are the threads damaged or is there some dirt on the threads?

    Pat Ireland
     
  10. KENENT1

    KENENT1 Active Member

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    everything is clean, the end of the tube that seats in the barrel only has about a .005 to .007 flat to seat in the barrel, I wonder if I could have over tightened the tubes, and wore a little ring on the shoulder they seat on......1/4 of a turn is only .010 too deep.


    tony
     
  11. KENENT1

    KENENT1 Active Member

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    Pat, they seat on the bottom,the tube dosen't touch the muzzel, I marked the tubes after checking them on a concentricity gage.



    tony
     
  12. Pull Bang

    Pull Bang Member

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    Tony

    Not sure that altering the base of the choke tube will accomplish the desired result or is the best thing to do.


    Choke tubes must seal on the ledge of the ID of barrel in order to keep the gases from escaping around the choke tube. If you alter, grind away the end of the choke tube you may be asking for trouble. (?)

    Ever have a choke tube work loose and go unnoticed. You clean your gun, discover the loose tube and remove it. You will see burnt black carbon built up on the OD of the choke tube.


    I would not alter the choke tube but contact the manufacture and go with their advice.


    Good luck,


    Frank
     
  13. KENENT1

    KENENT1 Active Member

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    Frank, there is already alot of carbon that builds up on the od of the tube...I can machine the tubes flat, I owen a machine shop, and this would be an easy cut.

    the barrel is already cut crooked, that is why Beretta is replacing it.


    tony
     
  14. g7777777

    g7777777 Active Member

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    were they made for that specific barrel?

    I have used them and never had a problem in the barrel they were made for

    they only work as intended in the barrel they were made for

    they wont even work in the bottom barrel of an O/U if made for the top barrel

    If they were made for that barrel- do as suggested- call briley or return them

    If they werent made for that barrel- dont expect results to be what you want- order some new chokes

    regards from Iowa

    Gene
     
  15. KENENT1

    KENENT1 Active Member

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    Gene, I sent the barrel to Briley last summer to have these tubes made, it seems strange that they both would be almost exactly the same amount too deep, I'm starting to think that maybe they were seating on the chamfer above the threads instead of on the end that goes in the barrel, over a period of time the chamfer has screwed farther into the threads and know they are seating where they should be.

    there is only .008 to .010 differance on the depth.

    tony
     
  16. g7777777

    g7777777 Active Member

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    return the barrel and the tubes to them- they will fix it and probably will pay your shipping

    Gene
     
  17. redhawk44

    redhawk44 Member

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    If it was mine, I would apply a little BLUE locktight....I think it is called 404 and screw the tube in to where you know from experience it puts the pattern where you want it and let it go at that.

    The BLUE locktight will allow you to get the tube back out by the application of a LITTLE heat, that is to say that you don't need to get it hot enough to damage the blueing on the barrel.
     
  18. HSLDS

    HSLDS Well-Known Member

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    Tony,

    What is the chance that in cleaning you got the tubes placed back into the WRONG barrels??

    They were custom made for each barrel - that means they MUST be placed correctly - reverse the order and you may have the answer to your problem.

    David D
     
  19. KENENT1

    KENENT1 Active Member

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    Dave, these tubes were made for an unsingle barrel.

    today, I'm going to turn up an indexing spacer that will fit on the end of the barrel and under the knurled shoulder on the tube, looks like .o41 thick will do the trick.

    Just wish the new barrel would come in......tired of all the playing around just to get this $1600 barrel to shoot straight.


    tony
     
  20. HSLDS

    HSLDS Well-Known Member

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    Tony,

    Never said I could count.

    VERY tongue in check, but why don't you close your right eye... shoot left eye only - should give you the displacement you want.

    Good luck with the project.

    Happy New Year

    David D
     
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