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Thread: Fire Lapping

  1. #1
    Boolit Mold songdog33's Avatar
    Join Date
    Nov 2009
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    Boulder City, NV
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    16

    Fire Lapping

    Hello: I was given a jar of LBT fire lapping compound from a friend. There were no instructions with it. He used it to fire lap a couple of .22LR guns he had. I was interested in using it on my .44 Mag Ruger Super Blackhawk. It has a little bit of a constriction in the Barrel where it is screwed into the Frame. I was wondering about what kind of bullets to use for this, Should I cast some pure lead bullets for this, and what kind of load would i use for fire lapping? I have a Lyman 429421 mould. How should I size them for this operation? I thought about buying the LBT lapping bullets but thought that they can't be anything special that I can't do myself. Any insite would be greatly appreciated. Thanks, Tom

  2. #2
    Boolit Master

    curator's Avatar
    Join Date
    Mar 2006
    Location
    Fort Myers, Florida
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    758
    You might check Veral Smith's web site:http://www.lbtmoulds.com/aboutus.shtml
    Fire lapping is pretty easy and works well for removing the "thread constriction" on Ruger revolvers, I have successfully lapped out the .002" choke at the beginning of the bore on my two Super Blackhawks with the LBT compound.

    First: the lapp bullets need to be slightly larger than the biggest diameter of your bore and made of material about 12BHN. Wheel weight alloy after 2 weeks of age hardening are perfect. Harder or softer bullets may not work as well. Be sure your chamber throats are slightly over bore size as well or this process will not work as planned.

    Next: Roll the bullets between two steel pr glass plates to embed the compound into the sides of the bullet. No need to fill the grooves.

    Next: Using fired, reprimed and unsized cases, load grit-embedded bullets over a small charge of fast buring powder. I used 2 grains of Bullseye in my .44 Mag, but you may need a bit more or less. Best results are obtained if the bullet can actually slip down inside the case and has enough velocity to exit the bore but not much more.

    Carefully load and shoot five lap-rounds making certain that the bullet exits the bore each time. Go slow, clean and check you progress after each five rounds. Try to keep the grit off the outside of your cases while doing this. It took 50 fire lapping shots to clear the choke on my SBH. I checked results using a .445 pure lead round ball after each five shots.

    After successful fire lapping my revolvers have had a significant increase in accuracy with cast bullets and a slight increase with jacketed. However, copper and lead fouling is a thing of the past.

  3. #3
    Boolit Master
    Join Date
    Feb 2007
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    The deep south,... of Vermont!
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    Curator gave you a good set of directions. I have done several, and have been well pleased in each instance.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check