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Thread: Washed out breech end..........

  1. #1

    Washed out breech end..........

    Washed out breech end..........


    CYA friends:


    The biggest problem we have today with the folks who produce taper lapped, production, RFBR barrels is this:


    They spend so much time lapping the breech end, that it gets "washed out" as they attempt to induce the taper.



    So what can be done to correct this?



    Your friend, Bill Calfee

  2. #2

    Exterior profiling?

    Mr. Calfee,

    I believe I have read a couple of times that you feel results from profiling after the button goes through the barrel, such as say reverse tapering, produces inconsistent results of internal bore tapering. Can you describe how a typical bore feels after it has seen external profiling of say reverse tapering? Even though the results may be inconsistent, would it get us closer to a properly taper lapped bore without the breach being washed out because it would take less lapping work to obtain a steady transition/taper from breech to crown? I have not had the opportunity to try reprofiling a barrel to something like a reverse taper to see for myself what happens. It may be unworkable I just don't know.

    Tad

  3. #3

    Friend TE

    Quote Originally Posted by Tad Earhart View Post
    Mr. Calfee,

    I believe I have read a couple of times that you feel results from profiling after the button goes through the barrel, such as say reverse tapering, produces inconsistent results of internal bore tapering. Can you describe how a typical bore feels after it has seen external profiling of say reverse tapering? Even though the results may be inconsistent, would it get us closer to a properly taper lapped bore without the breach being washed out because it would take less lapping work to obtain a steady transition/taper from breech to crown? I have not had the opportunity to try reprofiling a barrel to something like a reverse taper to see for myself what happens. It may be unworkable I just don't know.

    Tad

    _____________________


    Friend TE:


    Douglas button rifled blanks are not lapped.


    To find out how the bore of a barrel feels that has been taper profiled after buttoning, all one needs to do is to slug a #1 Douglas taper blank for a Mauser or 700 Remington or any large barrel thread action.


    When you start pushing the slug from the enlarged breech end, once the slug gets to where the taper starts, it gets easier and easier to push until it gets to the muzzle end of the blank.


    A reverse taper will do the opposite, it will get tighter and tighter as you get toward the muzzle end.


    BUT............................


    There's always a but..........


    When the outside of the bore is profiled down, even if one starts with an absolutely, perfectly buttoned bore, the bore is not uniformly distorted.


    Therefore, lapping a taper profiled bore is doubly more difficult than lapping a straight profiled bore.


    ________________



    Tad, every interested shooter needs to slug a button rifled bore, I'm talking about a straight profiled bore here, before it is lapped.


    The slug jumps and jerks as it is pushed through the bore.


    Two things are in play here:


    Even with the finest of steel, and even with the bore reamed very uniformly, the button process leaves the bore jerky......


    Then when the profiling is done, this jerky condition is magnified.



    So the first thing the lapper has to do, at least it's the first thing I do when I lap, is to size the bore uniformly, then I start the taper lapping.


    So imagine the difficulty of getting a jerky, tapered bore uniformly sized before inducing the taper.


    By the way, this is an issue that must be dealt with when lapping sporta barrels.


    The original Calfee sporta profile has some reverse taper in the profile.


    The Calfee 2nd generation sporta profile, that Shilen produced, has no reverse tapering in the profile...


    This is why I believe the Calfee 2nd gen profile is superior to my original sporta profile.


    They are so much easier to properly taper lap.






    ____________________



    Tad, I'll tell you how bad an "as buttoned" bore feels with this story:


    I have unlapped Shilen octagons and ratchets, and some unlapped Broughton 4-C's, and several unlapped Douglas blanks left.


    All of these bores are jerky when slugged, because they were sent to me purely "as buttoned".


    Dan Muller, on the other hand, takes so much pride in his barrels, that when he sends me unlapped blanks, of which he's sent me quite a few, he always casts a lap and removes the bulk of the jerkiness.


    By the way, Shilen, Broughton and Douglas also take pride in their barrels, but, I asked for unlapped blanks so that's what they sent.


    But Dan Muller won't do that.....


    In conclusion:


    The reason we've went to .750" diameter barrel threads in our RFBR actions, is to allow us to use straight, non taper profiled barrels.



    Your friend, BC



    _____________________


    PS:


    Tad, Dan told me part of the jerkiness was due to some slight scale that forms in the bore during normalization...(heat treatment after buttoning)

    I advised Dan not to worry about it as I would take care of it, but, he simply would not allow one of his barrels out of the shop like that.


    As a matter if fact, I fit one of his barrels without doing any lapping, and it shot quite well....

    It was a 30 or 32 inch blank, so after I ran the test, unlapped, I then set it up and taper lapped it, shortened it and re-chambered it, and it
    turned out to be a killer.
    Last edited by Bill Calfee; 06-08-2019 at 12:13 PM.

  4. #4

    Washed out breech end

    Washed out breech end


    CYA friends:


    There's no way I could taper lap bores for a living.


    I couldn't even straight lap bores for a living.....


    First of all, taper lapping a bore is art, on top of all the hard work.


    Straight lapping a bore is just plain old hard work........by a careful workman to produce quality.



    The main difficulty in taper lapping is controlling the breech end of the bore since so much more lapping is done there.


    Which means it's very easy to wash out the breech end of the bore.


    CYA friends, I've seen so many new blanks, from all makers, washed out in the breech end.


    And I can understand this, because of the demand.


    I've got to say this again:


    I can't imagine taper lapping bores for a living.....


    _________________



    In my opinion, the number one rimfire accuracy barrel today is the Muller corrugated 8.


    And here's one of the reasons why:


    The corrugated 8, for whatever reason(s), can be successfully taper lapped, without washing out the breech end.


    I've now seen, and evaluated, several Muller corrugated 8's........all with beautiful breech to muzzle tapered bores, and not a single one has had the breech end washed out.


    CYA friends, I've got a suspicion as to why this rifling pattern is so easy to taper lap properly, without washing out the breech end.



    One other thing:


    Are Shilen ratchets and Muller 4-MI's capable of being killers? ( and also the Shilen octagon to a lesser degree)


    Of course, just look at the record books....


    But, those rifling patterns are much easier to wash out the breech end during the taper lapping, than the Muller corrugated 8.



    Your friend, BC

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