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Thread: Lee 6 Cav 401 - Why fins at the bottom all of a sudden?

  1. #1
    Boolit Bub
    Join Date
    Nov 2007
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    67

    Lee 6 Cav 401 - Why fins at the bottom all of a sudden?

    So I'm low on 40SW reloads so start casting some last night, I'm using a Lee bottom pour pot with a PID set at 750, using COWW. Everything is going along fine, I've done about 500 or so and topped the pot off a couple times. I top the pot off when it's about 1/3 to 1/2 empty, wait for the temp to reestablish and start back casting. I immediately start getting the below, "finning" at the bottom, like the sprune plate is warped all of a sudden. What causes this and how do I fix it? I've cast thousands and thousands with this particular Lee .401 and never had a problem. Appreciate any help or insights.....did some searches but my google-fu is failing me. Thanks!

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  2. #2
    Boolit Bub
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    May 2019
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    Mine did that, had to tighten down the sprue plate and it fixed it right up

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  3. #3
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    JonB_in_Glencoe's Avatar
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    Over heating the sprue plate is what causes it to warp, BUT if mishandled the sprue plate can bend when it is open. Either way, the cure is a new sprue plate.

    Also, I've had "Galling" under the sprue plate pivet screw, due to poor lubrication, create finning. The cure is removal of the sprue plate, clean and reface the top of the mold, then reinstall in reverse (putting the hinge bolt on the opposite end).
    ~~~~~~~~~~~~~~
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  4. #4
    Boolit Grand Master tazman's Avatar
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    I have had this problem when trying to run a long casting session and get as many boolits out as I can. Sometimes the speed is the problem.
    When the mold is running really hot and you are filling the mold quickly with a heavy stream of lead, this will sometimes push lead out under the sprue plate and give you those fins.
    What I do to stop this is run a smaller stream of lead so the cavity dosn't fill as fast and try to cool the mold a bit more often. Think a wet towel to set the mold on for a few seconds.
    If the sprue plate is loose, it will also cause this.

  5. #5
    Boolit Master
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    Aug 2014
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    South Central PA
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    Yup. A loose or warped spruce plate causes this.

  6. #6
    DOR RED BEAR's Avatar
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    I have to go with tazman it can be speed . I go to fast and this happens slow down it goes away. If spruce plate is bent it would do it all the time. Does it happen all the time? You can always straighten out the spruce plate if bent straighten as best you can and use old sharpening stone to stone it flat. I have had to do this on a couple molds. But if you get some good and some bad its probably speed.

  7. #7
    Boolit Bub
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    Nov 2007
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    Solved.......Warped sprue plate seems to be what the problem is, see pic below. I swapped it with one from another 45 TC mold I don't use very often and it's back in business, just did another couple of hundred with no issues. I didn't drop it and since I was using a PID I don't see how I could have overheated it....I think what I might have done is forget and let the mold cool last night before I emptied it and when I opened it cold I bent the plate.....I can't think of any other explanation........lesson learned.

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  8. #8
    Boolit Grand Master tazman's Avatar
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    That picture sure looks like a warped plate. Those can be straightened with some judicious work with a soft hammer and a good, flat surface.

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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