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Thread: Removing "flashing" from base and sides of cast bullets

  1. #1

    Removing "flashing" from base and sides of cast bullets

    I'm just getting into casting and I have 8 Lee 6 cavity molds which seem to work really well once I get the molds at the correct temp. I sometimes get a very thin strip of lead running the length of the bullet sometimes up to the tip/point - this is b/c the mold might not have been clamped closed as well as it could be. The bullets are still the correct size though, so IDK how this "flashing" leaks out of the cavity.

    I also use a bullet sizing die for all my rounds to make sure they are the exact diameter needed for each gun. I'm doing .356" now for 9mm loads. I also noticed that I get some flashing around the base which is a very thin ring of lead that I can usually scrape off with my finger nail but when I'm working with 2,000-3,000 rounds, it takes a lot of time to do these individually. So I'm wondering if there is a way I can deal with all this flashing at once, maybe by tumbling or vibrating after running through the sizing die.?

    I'm planning on powder coating all the bullets so IDK if that changes anything. I think it makes it even more important to remove the flashing if I'm going to be powder coating them though.

    Just as a note, all these bullets are just for range/target shooting so they don't need to be super precise and accurate (though Ideally I'd like them close as possible). If anyone has any suggestions I'd really appreciate it!

  2. #2
    Boolit Buddy chutesnreloads's Avatar
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    2000-3000???,,, Think I'd throw them back in the pot and recast them watching for the flashing

  3. #3
    Boolit Buddy


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    It sounds like you may have a bit of lead on the mating faces of the mold. Just a touch will turn you boolits into winged angels. Lee molds have light sprue plates. You need to make certain that they are down tight. With a Lee mold be certain to push down on the handle when you break off the sprue. With a 2 cavity Lee when you tap the plate tap it with a bit of downward force. Other molds like NOE or Accurate have thicker sprue plates that don't warp like the Lees. Lee molds are great but there is a reason why they cost less.
    Nothing gets rid of tension like shooting your old computer with a 10 gauge.

  4. #4
    Quote Originally Posted by chutesnreloads View Post
    2000-3000???,,, Think I'd throw them back in the pot and recast them watching for the flashing
    Well I'd say that maybe 200 of the bullets have this, the rest are fine and the ones that do have it are not even that bad which is why I didn't notice them when I was casting them. The flashing around the bottom I think is b/c the sprue plate may need to be replaced on this mold.

    I'll probably sort through them quickly and pull out those with flashing and I might try tumbling them for a little while and see if that does anything to fix this just for future reference. Worst case I might just use an exacto knife to scrap the bottom and side as I did this when the flashing was 4-5x thicker than what I have now (when I first started casting, I had a bunch of bad casts with thick flashing).

  5. #5
    Boolit Grand Master

    gwpercle's Avatar
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    The "flashing" happens when two mould surfaces don't close completely , a mould should close with no daylight seen between the block halves and no daylight between the sprue plate and block top .
    Any time the blocks aren't closed , completely ... you get the flashing .
    Lead can smear on top of the blocks and you get the round flashing and a tiny splash of lead on a block face will hold it open and you get the flashing around the body and point .
    Watch what you are doing , keep top of blocks and underside of sprue plate completely clean of smears or any lead build up ... cutting sprues too soon smears the lead across the top .
    And watch mould faces for anything holding them apart and keep a good tight grip on the handles ... if you don't hold them together while pouring ...you get the flashing .
    Any badly flashed boolits can be remelted ...so it's nothing lost .
    Gary
    Certified Cajun
    Proud Member of The Basket of Deplorables

  6. #6
    Boolit Buddy
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    I have a little tool I use to clean any stuck lead flakes. Take a piece of large rifle brass (308, 30-06) and cut off the neck. Take a hammer and smash the neck end closed and it'll be sharp enough to scrape any bits of lead from inside the mold, and big enough to hold onto while wearing your gloves.

  7. #7
    Boolit Grand Master


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    "Flashing" will happen with the Lee 6 cavity moulds when, as mentioned, the mould blocks are not closed when the alloy is poured in. Since you have cast 2-3000 and only 200 +/- have the flashing I don't think there is anything on the face of the mould blocks.

    If the flashing is on the lower sides and the bottom of the bullets that indicates you were holding the sprue handle too tightly with the when those were cast.

    When you close the sprue plate on the mould block that are together back the handle off just a tad so the camming of the handle isn't pushing on the side of the mould block. Then don't hold onto the sprue handle at all when pouring in the alloy but just hold the blocks together with the mould block handles.

    If using a bottom pour w/o a mould guide it helps to jury rig a guide or something to for the mould to sit on while pouring. Keep the sprue plat 1/2 - 3/4" below the spout at the most. IF a ladle is used having something to sit the mould blocks on while pouring helps a lot also.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
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  8. #8
    Boolit Master


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    Take a green scrubbie to your mold halves.. A tiny piece of lead will hold them open. I toss bullets with fins back in And correct before moving on.

  9. #9
    Boolit Master
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    I have one mold that gives me a bit of flashing at the base. Just enough to be annoying when putting on gas checks. For that mold I put the bullets in a plastic jug and tumble them for a few minutes. Doesn't take much. Then I apply gas checks as usual.

    Sent from my SM-P580 using Tapatalk

  10. #10
    Boolit Buddy
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    Quote Originally Posted by downzero View Post
    I have a little tool I use to clean any stuck lead flakes. Take a piece of large rifle brass (308, 30-06) and cut off the neck. Take a hammer and smash the neck end closed and it'll be sharp enough to scrape any bits of lead from inside the mold, and big enough to hold onto while wearing your gloves.
    Are you using this brass case tool to scrap an aluminum mold or are you using it on Fe and/or brass molds? I'd be worried about scratching aluminum mold faces with a brass scraper. And for that matter I'd be reluctant to even uses brass on brass molds.
    Last edited by oley55; 05-03-2021 at 10:59 PM.
    “Some people spend an entire lifetime wondering if they made a difference in the world. But, the Marines don't have that problem.” Ronald Reagan


  11. #11
    Boolit Master 44Blam's Avatar
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    If it is just whiskers, those will break off just putting them in a bag with other boolits... If it is like a wing, throw back and fix the problem.
    God is great!
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    Y'all know the rest...

    WWG1WGA

  12. #12
    Boolit Buddy Castaway's Avatar
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    Check the alignment pin bushings, both male and female, to see if they’ve worked their way inward and are preventing the mould from closing completely

  13. #13
    Boolit Buddy
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    If lead is not observed on the faces of the mold halves, another frequent cause of Lee six-cavity molds producing flash is that the mold has warped.

    I use two six-cavity molds at a time in volumn casting and have found that after some thousands of bullets, they no longer close completely and light can be observed (hold the closed mold up to the light), shining through.

    Some Lee Six-cavity molds come with observable light between the halves, or between the sprue plate and the top of the mold halves. I just replace them when that happens instead of dealing with the frustration of dealing with bullets having flash.

    As long as Lee molds are so cheap, I can afford to do that.

  14. #14
    Boolit Master


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    https://www.mp-molds.com/product/357...e-groove-mold/

    This is my favorite and most used 9mm mold. I use Hi-Tek to coat the boolits. I've cast somewhere around 40K of boolits from this mold.

    If you adjust the sprue plate correctly you won't have problems with the base.

    You can also get a circular lead ring on a boolit when sizing it. This normally happens when the boolit is way oversized or out of round.


    I'm curious about sizing to .356. Have you slugged your bore? I've got a lot of 9mm firearms and .357 is what I size to. None of them that I slugged were smaller than .356
    NRA Benefactor.

  15. #15
    Boolit Man HP9MM's Avatar
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    Another cause not mentioned is having the lead too hot.
    I think I see a rip in the social fabric, Brother can you spare some ammo?
    Corb Lund

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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
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