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Thread: air pocket

  1. #1
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    air pocket

    I recently cast up a bunch of Lyman 315 grn .575 semi wadcutters.

    I was inspecting them and noticed many had an air pocket inside the tip of the hollow base.

    If you look inside the open end of the bullet, it is in the tip of the open end, right where the tip of the core that forms the hollow base is located.

    I am casting at 750 F +... sometimes up to 900 when I don't pay attention to the thermometer as the lead level drops, so it is not cold. I am using a lee 20 lb bottom pour furnace.

    I am thinking I am opening the valve too fast and not letting the air vent, but I am wonder what others might think. Some come out with no air pocket, but most have some amount of void, some much larger than others.

    Any suggestions?
    Always do what you always done and you'll always get what you always got.

    I have found some have many years experience, and some have one year of experience many times.

  2. #2
    Jim Brady Knap's Battery is offline
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    You may get arguments on this but a very long time ago I tried casting minnies with a bottom pour and gave up due to the same problems you describe. Went to the ladle and never looked back. I even tried the bottom pour for my 69 round balls and found that even though they look great from the bottom pour the weights run to a closer tolerance by using the ladle.
    I'm sure other's will say they have no trouble with the bottom pour but try the ladle method and judge for yourself.

    Jim Brady
    2249V
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    Jim Brady
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    CUM CATAPULTAE PROSCRIBEANTUR TUM SOLI PROSCRIPTI CATAPULTAS HABEANT

  3. #3
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    I did the same as Jim.
    Norm Gibson
    Charter member of the 1st South Carolina Vol. Inf. ACWSA

  4. #4
    matt's Avatar
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    i have used both methods while i like dipping for minnies it has to do more with the pot leaking. try holding the mould off center of the sprue hole letting the lead flow into the mould that should push the air out and limit the voids. i still get them no matter what i use and have found that if im not careful on my technique thats when they show up in great numbers.
    hope this helps.
    matt
    winslows battery 9975

  5. #5
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    Thanks. This all follows what I suspected, but sometimes some has a magic bullet answer.
    Always do what you always done and you'll always get what you always got.

    I have found some have many years experience, and some have one year of experience many times.

  6. #6
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    Well guys, here's another variable -- the furnace itself.

    For years I limped along with the leaky, recalcitrant Lee El Cheapo bottom-pour pots, and was plagued by these voids. Pour fast, pour slow, tilt the mould, hold it level -- no matter the variation I tried, I got bubbles.

    Then, last year I had enough with the Lee furnace, and plunged for an RCBS bottom-pour furnace. Voila! No more pockets!

    Why? Got me. I can't think of a good reason, other than the facts that the RCBS spout doesn't get leaded up like the Lee does, or the heat seems more consistent. All I can go by is the result, and the result is no more holes.
    Jim Strang
    Gen. W.T. Sherman's Bodyguard
    Midwest Region

    "I think the Union army had something to do with it."
    ― Gen. George Pickett, years afterward, on why his charge at Gettysburg failed.

  7. #7
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    Air pockets

    Have been using bottom pour pots for 30+ yrs and do get air pockets but have lessened them to a minimum. First someone told me yrs ago to cut back the point of the base plug to a flat, about a 64th to max of 32nd of an inch on a mold that was giving me this problem. This helped a lot. If the base plug point is already shallow keep the cut to a minimum. Also I found that by holding the mold half an inch or so below the pour spout and open the spout slowly so you don't get the full force of the lead flow will allow the air to escape better. Makes for a more consistent bullet weight also. Sometimes I tilt the mold slightly so the lead flow does not hit the tip of the base plug directly.

    These things seem to work for me. Sure, I still get a pin hole now and than. I just dump them back in the pot and keep going. I tried casting with a ladle when I first started skirmishing and found it simply too slow.

    Well, that's my 2 cents of advise! :lol: Might work for you. Have fun and don't get frustrated. It's all fun in the end!

    Chao,

    Dennis, 4th Ky Cav.

  8. #8
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    True

    If thou wants their balls to score,

    Ye must ladle pour !!!

    Philo
    Regards,


    Phil Spaugy

  9. #9
    Jim Brady Knap's Battery is offline
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    When loading for smoothbore





    take this advice






    The dipping in lube






    must be done thrice!





    Burma Shave






    Jim Brady
    2249V
    Knap's Battery
    Jim Brady
    2249V
    Knap's Battery


    CUM CATAPULTAE PROSCRIBEANTUR TUM SOLI PROSCRIPTI CATAPULTAS HABEANT

  10. #10
    RaiderANV's Avatar
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    This question comes up like every couple months. I tried all the answers and none really worked. The cut the tip of the base plug and holding the mold on the slight angle so the lead hits the sprue hole at an angle and the lead swirls in and the rest.

    My air pockets stop 99.9% of the time when I started pouring the bullets AND leaving a big pile of lead in top of the mold while pouring. I can only guess it's that lil extra weight that rids the air pocket.

    But then again I've cut bullets from different folks in half that looked just fine and found air pockets inside their rounds

    I wieghed the rounds with air pockets and they ranged 15 grians either direction. I then shot them all and the impact didn't change a bit so go figure.
    Never squat with yer spurs on!!!

    Pat "PJ" Kelly #5795V
    Virginny & Texas
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    MAYNARDS RULE!! & starr's DROOL!
    Hence the rust. MAYNARDAE LAUS DEO!

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