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Thread: Another question

  1. #1
    Join Date
    Sep 2014
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    Another question

    After reading numerous posts and comments on this I have to ask. Setting up a barrel for chambering in a long headstock lathe, it appears that some use a tight fitting bushing inserted in the bore of the lather and engaging the OD of the barrel for alignment. I can understand how to indicate in the chamber end but how does one ensure the chamber/muzzle relationship is accurate? We do know that the ID and OD of a barrel are not always concentric. How do they compensate for this. One cannot us the "gritter's" method because the muzzle end can't move. Am I missing something here or is the muzzle/bore runout of no consequence?

  2. #2
    Join Date
    Feb 2003
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    Houston, Texas
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    Quote Originally Posted by Jim Kobe View Post
    After reading numerous posts and comments on this I have to ask. Setting up a barrel for chambering in a long headstock lathe, it appears that some use a tight fitting bushing inserted in the bore of the lather and engaging the OD of the barrel for alignment. I can understand how to indicate in the chamber end but how does one ensure the chamber/muzzle relationship is accurate? We do know that the ID and OD of a barrel are not always concentric. How do they compensate for this. One cannot us the "gritter's" method because the muzzle end can't move. Am I missing something here or is the muzzle/bore runout of no consequence?
    http://benchrest.com/showthread.php?...ting+up+barrel

    You must turn a spot on the barrels OD at the muzzle that is dead true to the ID of the barrel.

    The hole in your headstock also needs to run true. Some do not. I doubt a couple of thousandths will make any difference.

    Look through the link I gave. It gives a step by step procedure with pictures.

    Just to recap, since the ID's of barrels are no where near truly straight, you need to pick two points to indicate and then have all subsequent machining operations run true with these two points.

    The Gordy method does this, but he is indicating points chosen at the chamber end, paying no attention to the position of the muzzle. I choose to keep the ID of the muzzle running true at all times, indicating what will become the throats area as the second point, then chambering and threading to match those points.

    Keep in mind, using my method, you must predrill to remove stock and then single point bore the chamber so that will run dead true with the two indicated spots. I basically use the reamer just to get the final finish and dimensions for the finished chamber.

    Also, you often have to compromise a little. I have seen barrels exhibit over .001 difference in just an inch of length up where the throat will be. That is very aggravating.

    By the way. Don't be frightened to actually check your work. Many don't, just assuming that everything will be ok. Don't assume anything.
    Last edited by jackie schmidt; 11-07-2017 at 10:28 AM.

  3. #3
    Join Date
    Sep 2014
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    53
    I missed the part about truing the OD with the ID and I guess that makes good sense. May I assume one would turn the OD to the same dimension as the bushing to make things a little easier/

  4. #4
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    Feb 2003
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    The muzzle end is not that important to be dead perfect centered in line. If it was then the Gritters method wouldn't work as very seldom is the bore anywhere close to the center line of the lathe bore with that method. What having the bore centered on both ends does do, is that it makes the barrel shoot close to the same spot when changing barrels from one barrel to the next. If you use the method of chambering a barrel where you move the muzzle around to get two points centered at the breech end, then there is no telling how far away the barrel is going to hit from one barrel to the next. I center both ends, at the muzzle and at the projected throat of the chamber. I've also chambered barrels by moving the muzzle around to get two points at the breech end indicated in. I've not seen any difference in how the barrels shoot whether done one way or the other. At the WBC I changed barrels, when I fired a shot on paper with the second barrel, it hit within two inches of where the other barrel was hitting. The odds of doing that when you move the muzzle around to get the barrel centered at two spots at the breech end are very unlikely. When I have a barrel that is too short to indicate in both ends, I have a dead center that uses a piloted bushing that will slip into the bore and slide down the spindle bore. The bushing keeps the barrel from sliding off the center. The dead center is locked into place with the four set screws tapped into the end of the spindle. You'll get a lot of answers on this of how various people do it. No one way is right and every other way is wrong. Just different methods to get similar results.

  5. #5
    Join Date
    Feb 2003
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    Tennessee
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    In chambering a barrel, why would you NOT want the bullet exit point (muzzle bore) not be in exact alignment with the rest of the assembly?? Several reasons to do so, one that Mike states above. No reasons I can think of not to do so.

    Using a lathe with a too long headstock makes this outcome more complex. My solution would be, on the muzzle end, cut it to within a fraction of its finish length, put it in a steadyrest and use a piloted center drill as so to get the center's surface true with the bore. Then with the muzzle end running on that trued center true the OD. Then make a bushing that holds that trued OD with the lathe spindle ID while cutting the chamber.

    A much earlier chambering method involved chambering using a steadyrest instead of chambering through the headstock.

    Better ideas??

    .

  6. #6
    Join Date
    Oct 2015
    Location
    Southwest VA
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    I have chambered barrels now using the long headstock method using bushings in the spindle bore on two different lathes. One 15 Leblond regal and the other a 15 inch Clausing Colchester with great results. Ive also used a steady rest and ive also used Gordy method. To each his own but i like dialing in the throat and muzzle on my South Bend Heavy 10. This method has given me the best on target results. I owe thanks to alot of folks on and off this forum.

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