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Thread: Need help with bullet quality in a Bottom Pour pot

  1. #1
    Boolit Buddy
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    Need help with bullet quality in a Bottom Pour pot

    First time bottom pour pot owner here. Also kinda frustrated.

    For the past 1.5 months I have tried dialing in the bullet quality of my RCBS pro melt 2. I dont think it's an issue with the pot, I think it's an issue with my "settings" for lack of a better term.

    I'm casting a 73 grain 227 bullet with a 6 cavity brass mold. (I have tried 2 other 22cal molds, one brass one aluminum, all with the same problems)

    When I bottom pour I get anywhere from 50-75% rejects. I'm pretty picky about my rejects. The most common rejects are based on the bearing band fillout (rounded in places or beveled) and little wrinkles in the lube groove nearest to where the mold closes. With a ladle pour I can get down to 10% rejects if I have my rhythm going really well.

    My process so far for trying out new settings is to adjust my mold guide, flow rate, and/or temperature on the PM2 and then cast 100 bullets with the bottom pour pot then 100 with the ladle out of the top of my PM2. With 100 225 bullets, the level of lead in the pot doesn't change much, but I get a decent sample size. Then after 100 of ladle pour, I go back to the bottom pour for about 50 bullets to make sure I was getting the same results as when I began.

    So it's the same alloy (cww+2%) and same temp for the two groups of 100 bullets. The alloy is super clean.

    I've tried, casting fast, casting slow, Temps as low as 690, as high as 750. The mold guide about .650 inches from the spout down to 1
    25 from the spout.

    With a bottom pour, there is something about the way the lead is delivered to each cavity that are causing these issues. I'm at my wits end of what to do.

    For the life of me I cannot find the sweet spot to get this bottom pour pot to cast consistent quality. I'd be fine with 25% rejects, in an ideal world 15% or less would be nice. The problem with my current results is that there is no time or effort saved when I have to recast a bunch more bullets.

    I have read many archive posts on the subject of ladle pour vs bottom pour. But what I do not see is an explanation of the settings everyone is using to get excellent quality bullets from a bottom pour pot.

    What are your secrets? How can I close the gap with my bottom pour quality to get it closer to a ladle pour.

  2. #2
    Boolit Master

    Mike W1's Avatar
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    I've never cast anything that small so take this FWIW. Noticed one mold is brass and they apparently are harder to get up to and keep at casting temperature. I'd suggest a hot plate for that as a remedy for one thing. I'd also lower the gap between spout and mold to about 1/4". Everyone seems to differ but I've always had my best results pouring directly into the sprue hole. Others let it run in and some have it swirl in. Either of which I "think" requires the sprue plate to be much hotter. Those latter 2 seem to require a much larger sprue than my way does. The Art & Science forum has some guys that pour 22's and could be of some real help to you. Also might try the CBA site.

    Even a 15% reject rate is pretty high. I only do pistol anymore and seldom have to reject anything but mine aren't the little itty bitty ones that are a lot trickier either. I'm sure one fellow over there bottom pours match quality 22's.
    Mike

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  3. #3
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    Preheat the mold on a hotplate set to 400°

    Pressure pouring on a bottom pour pot is like ladle pouring, Hold moth mold tight to the spout, pour lead, and keep pouring for a second when you lower the mold from the spout. This is a way to heat up a mold at the beginning of a casting session. When the mold gets hot you can go to the regular bottom pouring with the top of the mold 1/4 - 1/2 inch from the spout.

    adjust the flow of the lead to where it is fast but not too fast that you can't control the pour.

    leave a quarter size sprue puddle on top of each cavity.

    I like to "purge" the spout (squirt a little into the catch basin underneath to remove any cooler lead in the spout before each pour
    Last edited by Conditor22; 02-12-2021 at 09:36 PM.

  4. #4
    Boolit Grand Master In Remembrance
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    No fill out = mold too cold and with a multi cavity, have to keep the whole mold at temp. Plus, a 5 chondrites pour for each cavity and a large sprue puddle across the whole top of the mold
    Regards
    John

  5. #5
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    Mal Paso's Avatar
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    Might put the mold back on the hotplate while the sprues freeze to keep the temp up.
    Mal

    Mal Paso means Bad Pass, just so you know.

  6. #6
    Boolit Buddy

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    I prefer to ladle pour most of my boolits. Using a cast iron pot and coleman gas stove. This set up not having a temp control I just keep raising the fire till they fill out better.
    I cast two different heavy 225 boolits a 5 cavity 73grain and a 4 cavity 79 grain and when I'm using my old lyman pot the temp is set upwards to 825 for these. Its usually at 750 for other boolits with my alloy.
    When I'm using the bottom pour on these mold I also don't start and stop the pour at each cavity. I open the spout and hold it open till all the cavities are filled then stop the flow. Fill the first cavity then move the mold to the next hole leaving one long continuous puddle on top of the spru plate. This helps to keep it heated up more. And a good fast pace helps.

    Also what is the air temp where you are working. I get a lot more keeper when it's 90 degrees out versus 40 degrees that's why I do most of my supply of 225 boolits in the summer time. Its hotter out so the molds stay hotter.

    Don't be afraid to turn the temp up till you start getting frosted boolits. If this happen you can adjust the temp back down our slow your pace. Frosted Boolit should be well filled out and shoot just fine.
    Last edited by Kylongrifle32; 02-12-2021 at 06:18 PM.

  7. #7
    Boolit Grand Master Bazoo's Avatar
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    Mould temp, but also sprue size makes a difference here. Ladle casting I leave as large a sprue as I can without it running off the mould or into an adjacent cavity. If it runs, I'll get slightly rounded bands. If I have a small sprue with a small bullet, fillout isn't as good.

  8. #8
    Boolit Grand Master
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    Long narrow boolits seem to be the bane of bottom pour casting, which to my mind a 73 grain .227 diameter pretty much defines.

    I haven't cast any .22's that long, so this is primarily guesswork. Try setting your mold guide to about ¼" clearance, it could be the alloy is cooling just enough to cause problems with fillout.

    What I have done with all my bottom pour pots is to adjust them to where they work with most of my molds, then leave them alone. Some molds just seem to work better by ladle filling, I have had some that work better by pressure filling from a bottom pour though.

    Good Luck,

    Robert

  9. #9
    Boolit Buddy
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    I'll try to respond to many comments here, but first off thank you to everyone for your help and suggestions.

    I should start off and confirm that I always use a hotplate. I never start a casting session without having heated up my mold first. Settings are dialed in on the hotplate to I always get frosty bullets on the first pour.

    And as for mold temp, I'm getting frosty bullets by both bottom pouring and ladle pouring. So I know for sure we are in the frosty bullet range.

    I have cast as high as 750-760 when running the test of both 100 ladle bullets and one hundred bottom pour. Are we saying by nature of just bottom pouring I should crank to somewhere close to 800?

    I'm already doing big sprues when bottom pouring since I did notice that visual difference between the two methods. However, I have not gotten closer than about 5/8th of an inch to the nozzle.

    I have tried filling from front to back then back to front. For some reason filling the front cavity reduces the rejects by a little. I'm always continously pouring. No starting and stopping the flow.

    I do cast directly on center line of the cavities. I had not heard of the 'swirl' technique. Did some archives searching and I'm going to give that a try.

    Tonight or tomorrow morning I'll give a shot at a swirl super close to the nozzle.

    Can someone also give a little more detail as to what "pressure casting" is with a bottom pour pot?

  10. #10
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    Quote Originally Posted by Dimner View Post
    Can someone also give a little more detail as to what "pressure casting" is with a bottom pour pot?
    Move the guide out of the way.
    Hold the sprue hole on/up against the bottom of the pour spout.

    (Note how well they fit? Now ya know why the nozzle and sprue holes are shaped like they are)

    Fill both cavities, let the mold down and pour a sprue.
    Wear big gloves. You will get a little bit of splatter. It bounces up too.
    It doesn't work well if the mold isn't hot enough.
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  11. #11
    Boolit Master
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    With pressure casting, you place the sprue plate directly against the nozzle on the bottom of the pot. This naturally requires a start and stop of the flow.

    If you do a "running bead" type of pour, you are allowing the hot alloy to flow across the sprue plate and it is deflected across the hole, and might be blocking the air venting from the cavity. I do the start and stop, move to the next and repeat. I also start from the farthest hole and tilt it slightly lower so that over flow will flow away from the next cavity. If you are only 1/4" from the plate, you might get a tall sprue button and then have to lower the mold rest to remove the mold from under the nozzle. I like perhaps 3/8" or whatever height allows clearance after the sprue puddle becomes solid. I usually cast at about 720 Degrees and my shed is not heated so I usually do not work in temps of less than 40 degrees. Especially with the small caliber bullets. Adding alloy to the mold is adding heat and small bullets do not add enough heat on a cold day.

    Some sprue holes are a little on the large size and others can be smaller. The smaller the sprue hole, the nicer the bullet base can be and easier to cut the sprue. But that can cut down the flow into the mold. Compare the sprue plate holes with other molds and see if that could be restricting the flow and allowing the puddle too much time to cool before the mold is filled. Good luck, it will all come together with time and experience.

  12. #12
    Boolit Master
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    I can tell you but you will not like it , compression casting with a ladle /single cavity . It is nothing more than keep the ladle nipple mated to your mold and count to 10 . I said you would not like it but you will get 100 % fill with bases that would cut you and weights consistant with virtually no rejects . I do it for shooting long and can"t afford rejects as they waste powder and lead ,not brass (I shoot muzzle loaders) and single cavity is the only way to compression cast .A full ladle with the nipple pushed into the mold ,count to 10 and wait 5 before dumping sounds slow but it goes quick with practice .Try it and you will like it/Ed

  13. #13
    Boolit Buddy
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    Sorry I also forgot to mention I'm casting at a climate controlled 67 degrees.

  14. #14
    Boolit Master
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    I've never used a mold guide but have almost always bottom poured. It's a feel and learn thing to know how close to the spout you need to be depending on the mold, temps and alloy.

  15. #15
    Boolit Buddy
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    Quote Originally Posted by Dusty Bannister View Post
    With pressure casting, you place the sprue plate directly against the nozzle on the bottom of the pot. This naturally requires a start and stop of the flow.
    That's the only way I can get my .22 molds to fill out. I don't add additional lead on top after the cavities are full. You can try it with and without extra sprue and see which works for you.

  16. #16
    Boolit Man
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    I have a RCBS Pro Melt II. If I run it less than 820 degrees, I don't get good bullets. I don't think the temperature controller is accurate.

  17. #17
    Boolit Buddy
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    As others have mentioned ... mold temp. When I cast for .224 it is a pain ... I gotta move fast and keep the mold hot. When casting for 45-70 I can take a coffee break and still get a good cast.

  18. #18
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    Take a butane lighter and lightly smoke the mold cavities.
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  19. #19
    Boolit Grand Master

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    While the alloy is in the pot they are all perfect its when you pour them in the mould the problems occur.

    Try preheating the mould on a hot plate nit just to a certain temp but to temp and then 15-20 mins to normalize thru
    Then pour as large a sprue as possible. shield the casting area from drafts and breezes. Theres not a lot of mass in these bullets to keep the blocks hot.

    Also check the vent lines and clean blocks well. Everything has to be right when casting these smaller bullets in blocks with more mass than the bullets have.

  20. #20
    Boolit Buddy
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    What I don't understand about all this is why is my mold temperature perfect when ladle pouring, but not perfect when using the exact same variables (including mold temp) with a bottom pour.

    It's just strange.

    I wonder if some one could make a bottom pour spout that didn't pour straight down, but poured more on an angle to simulate the geometry of the ladle pour. As in a spout that delivered the alloy on a 45 degree angle or something like that.


    But I still need to try some other things first. Mainly the sprue touching nozzle pressure cast technique

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