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Thread: Lapping and bumping

  1. #1
    Norway
    Guest

    Lapping and bumping

    Guys, I can't get in on my regular name, Řyvind. I've tried a bunch but no action from the site managers. So here it goes. How do you "bump" a lapp? I've got a screw on the lapping head to tighten after the lapp loosens. But what do you do to "bump" a regular rod and lapp? Řyvind from Norway

  2. #2
    Quote Originally Posted by Norway View Post
    Guys, I can't get in on my regular name, Řyvind. I've tried a bunch but no action from the site managers. So here it goes. How do you "bump" a lapp? I've got a screw on the lapping head to tighten after the lapp loosens. But what do you do to "bump" a regular rod and lapp? Řyvind from Norway
    I don't know how to do that but did reset your password. Try it when you get a chance.

  3. #3

    Friend Norway

    Quote Originally Posted by Norway View Post
    Guys, I can't get in on my regular name, Řyvind. I've tried a bunch but no action from the site managers. So here it goes. How do you "bump" a lapp? I've got a screw on the lapping head to tighten after the lapp loosens. But what do you do to "bump" a regular rod and lapp? Řyvind from Norway

    Friend Norway:

    If this is Oyvind, how long is your lap with the screw in it?

    Your friend, Bill Calfee

  4. #4

    Length of lapp.

    Quote Originally Posted by Bill Calfee View Post

    Friend Norway:

    If this is Oyvind, how long is your lap with the screw in it?

    Your friend, Bill Calfee
    Hi, I'm back :-) I've made it about 2-3 inches long on a round brass jag taken down to 4mm about. Hard to get long enough, but I had to try. Otherwise the length is usually 3 plus on a rod I got from Anschütz. I've gotten some Lothar Walther blanks, and they really need lapping.

  5. #5

    Friend Oyvind

    Quote Originally Posted by Řyvind View Post
    Hi, I'm back :-) I've made it about 2-3 inches long on a round brass jag taken down to 4mm about. Hard to get long enough, but I had to try. Otherwise the length is usually 3 plus on a rod I got from Anschütz. I've gotten some Lothar Walther blanks, and they really need lapping.
    Friend Oyvind:

    You only bump up the ends of a lap...........no matter whether one is physically bumping up the lap, like me, or, like you, tightening a screw to do it...

    The major lapping of the bore must be done with long, non-deteriorated laps.....

    But, if you use one of these long laps too long, you will start to round off the tops of the lands....

    Therefore, at some point in the lapping process, one must reduce the length of the lap, to about 1-1/4" in length, then start the bumping-up process......

    The bumping up process, is actually a "finishing" process, to make sure the lands maintain their shape......

    ____________________________


    Lapping is an art......................

    I don't see how any human being, could possible do it day in and day out, and keep up the pristine quality, without going nuts....

    This is why all RFBR schmidts, who half way expect to turn out consistent winners, must be perfectionists in the art of lapping...

    Your friend, Bill Calfee

  6. #6

    Friend Oyvind

    Quote Originally Posted by Bill Calfee View Post
    Friend Oyvind:

    You only bump up the ends of a lap...........no matter whether one is physically bumping up the lap, like me, or, like you, tightening a screw to do it...

    The major lapping of the bore must be done with long, non-deteriorated laps.....

    But, if you use one of these long laps too long, you will start to round off the tops of the lands....

    Therefore, at some point in the lapping process, one must reduce the length of the lap, to about 1-1/4" in length, then start the bumping-up process......

    The bumping up process, is actually a "finishing" process, to make sure the lands maintain their shape......

    ____________________________


    Lapping is an art......................

    I don't see how any human being, could possible do it day in and day out, and keep up the pristine quality, without going nuts....

    This is why all RFBR schmidts, who half way expect to turn out consistent winners, must be perfectionists in the art of lapping...

    Your friend, Bill Calfee
    Friend Oyvind:

    I put one of my sentences on bold yellow.......above...


    If one tried to bump up a 4 inch lap, or a three inch lap, only the ends will get bumped up......you can not change the middle of a lap, that long, by bumping it up, WITHOUT STICKING THE LAP IN THE BORE.........

    If you ever stick a lap, it has to be melted out.........which don't hurt anything, it's just a hassle and a mess....

    ________________________


    Bumping-up a lap is art, simply because of the possibility of sticking it in the bore.......

    But, if one expects to taper lap a bore, while at the same time keeping the breech end pristine, you must bump up the laps.....

    The art of bumping-up a lap is better than casting a bunch of new laps, because, every time you cast a new lap it must be charged, which takes several applications of grit with the lap pulled back through the muzzle each time..............

    I've never lapped an unlapped bore, properly, with just one single lap......it does take casting two or three............depending on how much work you have to do to finish the bore.....

    But, one wants to do the entire lapping with as few, new, cast laps as possible......hence the bumping up process....

    Your friend, BC

  7. #7

    Bumping

    Ok, I think I get it, I can work around the issues and just work with it. What are the differences regarding chrome barrels vs. stainless? The ones I have done recently are AISI 420 and workable, but it takes time :-)

  8. #8

    Friend Oyvind

    Quote Originally Posted by Řyvind View Post
    Ok, I think I get it, I can work around the issues and just work with it. What are the differences regarding chrome barrels vs. stainless? The ones I have done recently are AISI 420 and workable, but it takes time :-)
    Friend Oyvind:

    Chrome m rimfire barrels will outlast stainless rimfire barrels....probably by a goodly margin....

    And as for lapping chrome verses stainless, I can lap either..........

    But, chrome m barrels are so much harder for the average RFBR schmidt to chamber/finish properly......

    Chrome m rimfire barrels are about as difficult to fit, properly, as are cut rifled rimfire barrels...

    And no one uses cut rifled rimfire barrels.....that is, if they expect to have a chance to win...

    _________________________


    Chrome verses stainless RFBR accuracy class barrels:

    Chrome will give many more rounds, if, one can fit one as simply as one can a stainless rimfire accuracy barrel, but, that can't be done....without considerable time investment and skill by the schmidt.....

    __________________________


    Therefore:

    The world of rimfire accuracy is not going to see an influx of chrome m barrels........winning.

    Just like the world of rimfire accuracy is not going to see an influx of cut rifled barrels.......winning.

    ____________________________


    Friend Oyvind, the world of "serious" rimfire accuracy is now, and will be in the future, dominated, totally, by stainless barrels...

    Your friend, Bill Calfee
    Last edited by Bill Calfee; 09-06-2016 at 09:54 PM.

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