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Thread: Friend Bill Johnson

  1. #1

    Friend Bill Johnson

    Friend Bill Johnson


    Friend Bill Johnson:


    I've started a new thread because the other thread about this subject was getting way too long....


    I did get a good close-up picture today....showing what one sees when they try to measure leade length using a dial caliper, and, showing the actual beginning of the leade, which one can not visually measure....cause it can't be seen with the naked eye....most generally...


    But before you look at the picture, I think I need to post some chamber design information.....



    My chamber that I designed years ago is very simple....


    It's .2250" diameter, straight sided, no taper, with a 2 degree leade......and it does not cut for the rim so I can vary the depth as I need to for different rifling patterns and various bore and groove sizes...



    Here's the part that most folks probably overlook:



    When you have a .2250" diameter chamber at the beginning of the leade, then a straight 2 degree angle into the bore of a barrel like yours, with say a .2218" groove diameter....( land top to land top is the bore diameter)


    This means there is .0032" of the leade free cut before the leade actually starts cutting the lands proper...


    Or, .0016" per side of the chamber.....


    So this area is not land cut when a bullet is inserted then removed....


    So, if one tried to measure the leade length with a dial caliper, visually, this free cut of the leade in not seen, nor measured....


    Now, here's the picture:



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    Bill, if you look closely you can see the actual start of the leade.....it's a very faint line just ahead of the wax groove that's just in front of the case mouth/crimp....



    By the way, this chamber is in a 6 groove Douglas barrel......

    Oh, and one other thing....

    This barrel has a perfectly center chamber, which you can tell by how even the faint line showing the beginning of the leade stays away from the wax groove just to the rear of it....look closely...

    If the chamber were not perfectly centered this faint line would vary in distance from the wax groove that's in front of the case mouth/crimp.



    Your pistol fool friend, Bill Calfee



    ______________________


    PS:


    Bill, I enlarged the picture so you can better see the faint line where the leade actually starts..

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  2. #2

    Leade Picture

    Hello Mr. Calfee.

    The picture you posted above is very clear. I can see the wax ring that you described. Electronic magnification is easier on my old eyes than a magnifying glass.

    I have no knowledge of chambers and bores. Your illustrations are very interesting and helpful.

    Thank you for taking the time to explain the dimensions and concentricity of a chamber to bore.

    Bill

  3. #3

    Friend Bill Johnson

    Quote Originally Posted by Bill Johnson View Post
    Hello Mr. Calfee.

    The picture you posted above is very clear. I can see the wax ring that you described. Electronic magnification is easier on my old eyes than a magnifying glass.

    I have no knowledge of chambers and bores. Your illustrations are very interesting and helpful.

    Thank you for taking the time to explain the dimensions and concentricity of a chamber to bore.

    Bill

    ___________________________


    Friend Bill Johnson:


    You're welcome.....


    Bill, I went to the shop today and took several pictures showing how to accurately measure the leade length....


    I've got to edit them, and do some typing....


    But...................



    Tomorrow in St Louis there's an ARA Area Tournament with a great deal of significance to the world of SAP ignition RFBR guns...


    So far this year all of the ARA Area Tournaments have been won by MD-PAS ignition guns...


    So there's a bunch on the line in St Louis tomorrow...


    Therefore.............



    I'll edit the pictures and type up the report and post it sometime Sunday...


    Your pistol fool friend, BC

  4. #4

    Friend Bill Johnson

    Friend Bill Johnson


    Friend Bill Johnson:


    I can only post four pictures per post, and I have more than that, so I'm going to go ahead a post a couple now...



    What these pictures are, is me measuring the leade length by using a dial caliper and visually measuring the land cuts in the bullet..


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    You can see that I got a reading fairly similar to what you got....


    Here's a close-up.....


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    I'll post the rest of the pictures and their explanation later today or tomorrow....


    Big match today in St Louis............a lot is at stake for our SAP ignition friends...



    Your pistol fool friend, BC

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