Rifle Re-Chambering Question - Page 2
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  1. #21
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    I think it is wise to leave the original barrel as is.

    Since you are planning a new barrel it would be an opportunity for you to shoot both old and new barrels to compare their relative performance. That way you can see for yourself how the extra care you put into fitting a new barrel pays off.

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    To be clear, other than the chamber not indicating concentric to the bore where you had the tip of the indicator- you have no idea if the barrel shoots, or not?

    I didn't see it mentioned above, but if you want to rechamber I believe it could be done by setting back enough and then boring the existing chamber to remove the runout and give a trued cylinder in which to start the reamer. Need to make sure that you can get the reamer pilot deep enough/engaged in the bore so it will run true.

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    Quote Originally Posted by tobnpr View Post
    To be clear, other than the chamber not indicating concentric to the bore where you had the tip of the indicator- you have no idea if the barrel shoots, or not?

    I didn't see it mentioned above, but if you want to rechamber I believe it could be done by setting back enough and then boring the existing chamber to remove the runout and give a trued cylinder in which to start the reamer. Need to make sure that you can get the reamer pilot deep enough/engaged in the bore so it will run true.

    I'll disagree a little. Assuming you are indicated coaxial with the bore and prebore to straighten your non concentric bore, your reamer bushing-pilot is superfluous. Your reamer will follow your bored hole that was cut indicated to your bore. The bushing can only follow a bore that runs out, maybe, beyond might start running out. If that happens your reamer will cut larger at the base of your chamber.
    I hope that is more clear than mud.

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    The OP has not really given much info. Per his post he indicated in 3 places total. He had the bore in 2 places so it appears that he considers those 2 correct and a datum for the chamber. BUT, is the neck concentric to the bore he has indicated ? Is the case head concentric with the bolt face? He needs to indicate the neck of the chamber, if those are within a thou or so that is probably as good as it gets. If the chamber really takes off at an angle to the bore that should be visible. IF the bore is reasonably concentric to the barrel and the chamber to the bore then there is no problem. If the chamber is out that much it would possibly affect extraction. Measure everything and then we will know if in fact, there is a problem.

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    Quote Originally Posted by tdmidget View Post
    The OP has not really given much info. Per his post he indicated in 3 places total. He had the bore in 2 places so it appears that he considers those 2 correct and a datum for the chamber. BUT, is the neck concentric to the bore he has indicated ? Is the case head concentric with the bolt face? He needs to indicate the neck of the chamber, if those are within a thou or so that is probably as good as it gets. If the chamber really takes off at an angle to the bore that should be visible. IF the bore is reasonably concentric to the barrel and the chamber to the bore then there is no problem. If the chamber is out that much it would possibly affect extraction. Measure everything and then we will know if in fact, there is a problem.
    If I read his original post properly he measured the bore at the muzzle and 1/4" beyond the chamber. That indicates to me that he had it in the headstock. He said set up like this the chamber was out .008 from the bore indication. Maybe it could happen that the neck would be coaxial to the bore and the chamber out .008, but very highly unlikely.

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    Indicate the throat and the back end of the chamber true, disregard the muzzle. That should be plenty adequate for what you need.

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    Quote Originally Posted by Butch Lambert View Post
    If I read his original post properly he measured the bore at the muzzle and 1/4" beyond the chamber. That indicates to me that he had it in the headstock. He said set up like this the chamber was out .008 from the bore indication. Maybe it could happen that the neck would be coaxial to the bore and the chamber out .008, but very highly unlikely.

    Doesn't matter what black magic system he used if his numbers are accurate. You cannot compare concentricity of two cylinders with less than 4 indications. If the chamber's indications are concentric to the bore, no problem. If the chamber neck is and the case head is out, maybe a problem. If it shoots well, no problem.

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    Quote Originally Posted by tdmidget View Post
    Doesn't matter what black magic system he used if his numbers are accurate. You cannot compare concentricity of two cylinders with less than 4 indications. If the chamber's indications are concentric to the bore, no problem. If the chamber neck is and the case head is out, maybe a problem. If it shoots well, no problem.

    TD, As I read it when he indicates the bore at the muzzle and the bore at the breech and they are coax or concentric to each other and then the chamber runs out .008". Correct me if I read it wrong.

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    You might be right, again, not enough info. He said he indicated the bore and that establishes 1 axis. He said that then he indicated the chamber and it was out .008". I took that to mean one indication of the chamber, location unknown. If it's that bad a job then it's unlikely that the entire chamber would be out the exact same amount. If he just ran a sweep of the breech end then it might be out more than the bore end but .oo8: seems like a lot. If the neck was out .008 to the bore I think that might be visible just looking through it. He needs to tell us exactly where he measured and what he got.

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    Quote Originally Posted by tdmidget View Post
    You might be right, again, not enough info. He said he indicated the bore and that establishes 1 axis. He said that then he indicated the chamber and it was out .008". I took that to mean one indication of the chamber, location unknown. If it's that bad a job then it's unlikely that the entire chamber would be out the exact same amount. If he just ran a sweep of the breech end then it might be out more than the bore end but .oo8: seems like a lot. If the neck was out .008 to the bore I think that might be visible just looking through it. He needs to tell us exactly where he measured and what he got.
    TD, I want to think he was indicating a factory hammer forged barrel. If that is the case it was not cut with a reamer.

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    Wouldn't a hammer forged barrel have the chamber and bore integral? How could they be out .008"? If only the bore was forged then we still need 4 indications to establish concentricity or cylindricity.

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    I have read, I think, that some companies forge the chamber and some do not. Its possible the bore is curved so the chamber shows run out even though it might be aligned to the bore at the throat. Would have to be a lot though, I think.

    It's also possible he's warped the barrel in the spindle by tightening the screws up before getting it true.

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    Quote Originally Posted by wesg View Post
    I have read, I think, that some companies forge the chamber and some do not. Its possible the bore is curved so the chamber shows run out even though it might be aligned to the bore at the throat. Would have to be a lot though, I think.

    It's also possible he's warped the barrel in the spindle by tightening the screws up before getting it true.

    Don't know where my previous post disappeared.
    Member said it was a Remington 700. They are hammerforged. He could warp it if using chuckjaws, but if he chambers as I, a cathead on each end of the headstock with copper inserts it won't bend the barrel.
    Last edited by Butch Lambert; 12-05-2019 at 10:11 AM.

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    Quote Originally Posted by wesg View Post
    I have read, I think, that some companies forge the chamber and some do not. Its possible the bore is curved so the chamber shows run out even though it might be aligned to the bore at the throat. Would have to be a lot though, I think.

    It's also possible he's warped the barrel in the spindle by tightening the screws up before getting it true.
    Using a cathead at each end of the spindle can definitely bend the barrel if the wrong technique is used. As wesg wrote, the screws have to be tightened very carefully after truing the bore. The potential for bending a barrel can easily be demonstrated, after the screws have been tightened enough for turning, by slacking all four outboard screws and observing how much resistance the still tight front screws are providing.
    Last edited by Tozguy; 12-05-2019 at 12:19 PM.

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    Quote Originally Posted by Tozguy View Post
    Using a cathead at each end of the spindle can definitely bend the barrel if the wrong technique is used. As wesg wrote, the screws have to be tightened very carefully after truing the bore. The potential for bending a barrel can easily be demonstrated, after the screws have been tightened enough for turning, by slacking all four outboard screws and observing how easily the barrel moves in the still tight front screws.


    You might want to rethink this. If you check it as you posted the screws on the left hand side of the headstock will allow the barrel to pivot and the weight of the barrel on the end of the headstock will allow it to drop slightly. It isn't being bent.

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    Say the screws are located in the 3,6,9 and 12 o'clock positions and the barrel is tight in both catheads and ready for turning. Then the outboard screws (on the left)are slacked off completely, what happens? The barrel would be easy to pivot in the front 3 and 9 o'clock screws but the front 6 and 12 o'clock screws would provide resistance to the barrel moving. As the outboard screws are retracted the barrel will bend some from gravity without moving in the front screws. Continue retracting the outboard screws and eventually the outboard end of the barrel will hang in the air if the front 6 and 12 o'clock screws are tight enough to hold it. It is easy to prove this by simply doing it.
    The point is that when setting up the barrel in the headstock if the front screws are tightened too much too soon any adjustments to the outboard cathead will be bending the barrel to some unknown extent depending on the amount of 'hold' in the front screws. It is a delicate operation to use just the right tension on all the screws to avoid bending the barrel.

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    Quote Originally Posted by Tozguy View Post
    Say the screws are located in the 3,6,9 and 12 o'clock positions and the barrel is tight in both catheads and ready for turning. Then the outboard screws (on the left)are slacked off completely, what happens? The barrel would be easy to pivot in the front 3 and 9 o'clock screws but the front 6 and 12 o'clock screws would provide resistance to the barrel moving. As the outboard screws are retracted the barrel will bend some from gravity without moving in the front screws. Continue retracting the outboard screws and eventually the outboard end of the barrel will hang in the air if the front 6 and 12 o'clock screws are tight enough to hold it. It is easy to prove this by simply doing it.
    The point is that when setting up the barrel in the headstock if the front screws are tightened too much too soon any adjustments to the outboard cathead will be bending the barrel to some unknown extent depending on the amount of 'hold' in the front screws. It is a delicate operation to use just the right tension on all the screws to avoid bending the barrel.
    OK sir, I just indicated a barrel in the headstock. I duplicated what you mentioned. It didn't bend the barrel. If it had, a Deltronic pin would not have slipped through the bore. My Deltronic pins are in .0001 increments.
    Carry on. This is turning into a pissing contest.

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    "Improved" chamberings ?

    How about hand turned reamers on a pull rod through the bore until the bolt closes ?

    Eliminates a lot of work.

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    Quote Originally Posted by Steven-Canada View Post
    "Improved" chamberings ?

    How about hand turned reamers on a pull rod through the bore until the bolt closes ?

    Eliminates a lot of work.
    You could do that after setting the barrel back. The headspace is shorter on a AI chamber. I would not object finishing by hand with a hand job.

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    Quote Originally Posted by tdmidget View Post
    Doesn't matter what black magic system he used if his numbers are accurate. You cannot compare concentricity of two cylinders with less than 4 indications. If the chamber's indications are concentric to the bore, no problem. If the chamber neck is and the case head is out, maybe a problem. If it shoots well, no problem.
    You can, but you'd have to know the form fault of the surface being measured. IE, how round is the round part. If we look at the flip side of this, a range rod is used, on the bore. Correct me if that is not correct. So, it is to 3 circumcised points, or at least five, since it would be a cylinder. I tried this example on a previous chambering thread. HK uses a fluted chamber. So, what is the run out? Is it concentric? Or even a spline on a shaft. The OP would need to index, ie mark the high spot. Rotate through. See if the high spot is in one direction only. I think some chambering processes do not use a piloted reamer.


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