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Thread: Reverse taper

  1. #1

    Reverse taper

    Reverse taper barrels, as I understand it, attempt to take advantage of the expansion effect of the bore when a barrel is turned down. So, you end up barrel bigger on the muzzle end than on the chamber end and a bore just the opposite. It seems, at least in theory, that such a barrel would not need as much lapping to get the desired tapered bore.

    In general if you look at a reverse tapered barrel you really don't notice it, so I have a question or three. To make it easy we have a barrel that is 1" at the chamber (yeah I know, too big, but we're making it easy) so what should it be at the muzzle end for the optimum reverse taper assuming a 28" blank? Or just think of it as increase in diameter per inch or something. Now considering that some barrels seem to be washed out on the chamber end due to lapping, would a 30" blank be better (so it could be cut off like he muzzle end and still get a fairly long barrel)? Finally, does anybody know if reverse taper really affects the bore much and, more importantly, if it does affect the bore, is it consistent?

    I know they're shorter but it almost seems to me that an good barrel for a non-sporter BR rifle may be a sporter blank which seems to be already reverse tapered.

    Any comments?

  2. #2

    new process

    shilen barrels are being special made starting with 1.200 at the breech and .900 at the muzzle end , then the whole blank is turned to .900 straight. This process should yield some internal taper before lapping thus not having to degrade the bore to get taper. I would love to hear Mr bill"s comments on this and what he thinks about Toms special barrels we recently received

  3. #3

    Friends wsmallwood and Jsmith

    Friends wsmallwood and Jsmith

    Yes, machining on the OD of a button rifled barrel does alter the bore.....


    Wally, you've asked some interesting questions, and Jsmith, you've shared an interesting bore finishing process.

    A question comes to my mind, here:

    Would it be easier to taper lap an "as buttoned" bore, (unlapped bore), if the bore already had a slight taper to it, than it would be to taper lap a uniform bore?

    And, with which method do I feel I could keep the breech end from being overworked and washed out, the best?

    _______________________


    Right now, before I comment further, there's two things I'd like to have happen.....because this is such an important subject.

    ______________________

    1. I wish Dan Muller would bring his thoughts about buttoning a non-uniform diameter blank.

    Because I'm not a barrel maker. So, although I have my opinion about this, it really wouldn't carry any weight in the discussion.

    ____________________


    2. I would like for everyone reading this, to be able to push a slug through an "as buttoned", (unlapped), rimfire barrel blank.

    ____________________


    CYA friends, there's a lot to think about here.....


    Could I produce a more pristine taper lapped bore if the bore had some taper to start with?

    CYA friends, you would think the obvious answer would be, yes.

    ____________________

    Here's something to ponder.....

    Once you get a couple tenths of taper, if you keep your lap full, so as not to wash out the breech end, which gets worked more, at some point you can no longer get the lap back to the muzzle end of the blank.

    And this happens whether you lap from the breech end, as I do, or the muzzle end, which some barrel makers do.

    _____________________

    So what if the bore, in the unlapped state, started out with that couple tenths of taper?

    A whole lot to ponder here.

    Your friend, BC
    Last edited by Bill Calfee; 10-06-2017 at 03:25 PM.

  4. #4
    Bill,

    I deal with things every day that have very obvious answers to the untrained eye. Those are things that I tend to pay particular attention to because the answer is often not so obvious. But, I admit, sometimes it is.

    Now to those who do not know the details of lapping a barrel and know something about the behavior of a bore as the barrel is turned down it may seem obvious that the barrel would be easier to lap or at least yield a more consistent taper. If it was really obvious then I would never have posed the question. There would be no need.

    My thinking is that perhaps there is an advantage in some way to reverse taper and perhaps it would yield a more consistent taper but then I think the bore must behave exactly the same way during that 26-30 inches of taper and I wonder if that really happens. The steel would have to be extremely consistent. Maybe it is.

    WS

  5. #5

    Friend wsmallwood

    Quote Originally Posted by wsmallwood View Post
    Bill,


    Now to those who do not know the details of lapping a barrel and know something about the behavior of a bore as the barrel is turned down it may seem obvious that the barrel would be easier to lap or at least yield a more consistent taper. If it was really obvious then I would never have posed the question. There would be no need.


    WS
    _________________

    Friend wsmallwood


    Wally:

    I've thought about the comments from Jsmith.......who says Shilen is inducing a taper to the bore by manipulating the profiling, before lapping.

    I have absolutely no doubt that this can be done......

    I do not know about the buttoning of a tapered blank......yes, this will affect the bore, I firmly do believe this.

    Here's my concern about buttoning a tapered blank, which by the way, I do believe will produce a tapered bore:

    Is the physical integrity of the rifling uniform from end to end, like it is when a uniform diameter blank is buttoned?

    __________________


    Wally, I know nothing about barrel making.....

    I do know that it would be physically impossible to "iron" a rifling pattern into a tube of steel..

    So, the bore of a buttoned rifle blank is larger in diameter, before being buttoned, than it is after it's buttoned.

    The rifling is not "ironed" into the steel...

    The steel is simply being displaced to form the rifling.....

    A .216" diameter bore, after buttoned, actually starts out at something on the order of .220" in diameter before buttoning.

    _____________________


    So, here's my concern about buttoning a tapered blank, as opposed to buttoning a uniform diameter blank:

    As the button passes through the bore, and meets less and less resistance from the tapered diameter of the blank, is the physical integrity of the rifling maintained uniformly end to end, like it is in a uniform diameter blank?

    Remember, the steel is being displaced as the blank is being buttoned.

    So, does the steel get displaced uniformly, so as to form uniform rifling, if a tapered blank is buttoned?

    ____________________

    Wally, maybe it does.....I simply do not know.


    Your friend, BC

    ___________________

    PS:

    The question still remains......

    Can a more pristine bore be maintained, breech to muzzle, if one starts lapping with a tapered bore, as opposed to starting with a uniform diameter bore?
    Last edited by Bill Calfee; 10-07-2017 at 02:35 PM.

  6. #6
    Bill,

    There's one key word here or two I guess and that's "physical integrity". It has to be maintained for a reverse taper to present a significant advantage.

    I think Shilen's new method of making a barrel as presented by Jsmith is interesting and may be a game changer. But I've only heard that here. It's not that I doubt it or think he's wrong, I just prefer to make decisions based on things that I know for a fact.

  7. #7

    barrel process

    wsmallwood, this is the way it was explained to me. I received one of these barrels along with Jeff patterson thru Tom Wilkinson. Jeff has told me Mr Bill has one also. Tom would be the man to get the absolute facts about this process as these were a special run of barrels that he had made. Jerry Smith

  8. #8

    Friends wsmallwood and Jsmith

    Friends wsmallwood and Jsmith

    __________________


    Friends wsmallwood and Jsmith:

    I've not discussed the details of these new ratchets with Tom...

    I have one and it's excellent...

    Jeff Patterson has evaluated the two he has, and told me they both were excellent.

    ___________________


    If, Shilen is doing what Jsmith believes they are, it could very well be the next big thing in barrels..

    If, Shilen is doing this proceedure, and if, when they button the tapered blank, the rifling integrity remains as uniform as it does in a uniform diameter blank, and if, there are no issues with lapping a tapered bore blank, this could very well be the next big thing in rimfire barrels...

    _____________________


    Friend Jsmith, I was at the range the other evening....

    Jeff Patterson was testing your Muller, Accu-Twist 4-MI barreled TCA triple lug.....

    Jeff allowed me to put a few round through it.

    If you'll feed that thing good stuff, and can point it, you can win any RFBR match in the world.

    That thing is stout....

    And that thing is kicking it with both Eley and Lapua.

    Your friend, BC

  9. #9
    So, this new process Shilen barrel is not just something anyone can order at this point? And I couldn't assume that if I did order a Shilen barrel it would be made using this new process? In other words, it's experimental at this point?

    Those are all questions not statements.

  10. #10

    shilen taper ratchet

    wsmallwood, These barrels are a special run that were made and I am not sure if any more will be made. Tom had them made and it took a long time to get them. They were made to his specs and I am to assume that only he knows the process for sure at this time. Mr Bill, I am for sure proud to get Jeff to do my gun and for it to have done well enough to get both of your attention. I will try to do it justice and thanks for your input along with Jeffs craftsmanship it means an awful lot to me. Jerry Smith

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