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Thread: Getting large molds to properly fill out. Tips?

  1. #21
    Boolit Grand Master

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    Flow is the key to casting big long bullets. You need to get the alloy in the mold before it starts to solidify. I cast alot of long heavy bullets, in the 1.125- 1.300 range from 38 cal to 45 caliber. Watch our sprue puddle it should take 4-6 secs to "frost" over.

    I cast these bullets with a ladle. Lyman or rcbs both have spouts opened to .205 dia from just under 3/16" much faster pour and better delivery. This modification greatly improved my results, with out raising temps or tin content.

    I believe it is more a result of bullet length than weight causing this. As the longer bullets start to cool sooner in the pour than the shorter ones, and the heat is less localized in the blocks.

    One difference in industry casting is those casting machines have a shot tube on them thats filled with the molten metal, then it pushes the material in under pressure filling the mould almost instantly, an option we dont have. The 'shot" goes in under several hundred psi and is held for a set time. This makes a mush better casting both in form and structure.

    I would recommend opening the spout up some on the bottom pour to increase flow or a modified ladle a described above. Warm your mould up to temp and cast a fairly brisk pace adjusting pace as needed. Workin the 700*-725* range and adjust from there.

  2. #22
    Boolit Buddy
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    Quote Originally Posted by Hanzy4200 View Post
    It's a aluminum 2 cavity and I am using a bottom pour. The pressure casting is a good idea, I've not tried that. The issue with adding heat is that the mold is already over heating within 4-5 casts at the current settings. At that point bullets are getting extremely frosted.
    If the alloy temp is reasonable, 700 to 750 i don't the the exact temp is critical. In my experience you cannot speed cast large heavy bullets. You simply overheat the mold. It is about casting cade.nce; you simply have to give the mold tome between pours to cool enough for the next pour. I'm sure everyone has his own method, mine is to pour then do a mental count (like a digit per second) until the sprue solidifies then cut, open and drop the bullet.
    I try to be as consistent as possible, cutting the sprue at the same count each cast. On a 530 grain bullet from an iron mold I might count 15 to sprue cut. If the mold seems s bit cool I'll decrease count to 14 or maybe 13. If at 15 the mold is showing signs of too much heat I increase the count until I find a happier medium. It just takes casting, being consistent and watching what the mold is doing ( what dropped bullets are like).
    A 2 cavity aluminum mold for big heavy bullets can be overheated very quickly. A 2 cavity IRON mold can be overheated if casting too fast so aluminum is going to get their sooner. You need to fill the cavity fast, leave a good puddle on the sp t ue plate like Larry said then experiment with time between pours to find where happy is. It could feel like too long between pours but good bullets is the goal.

  3. #23
    Boolit Grand Master popper's Avatar
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    Turn down the temp and make sure the vent lines are clean. My last mould from Tom had vent lines (IMHO) kinda in the wrong location - he uses a standard pattern. Had to smoke that one to get it to cast right. Break the top of the blocks, fine file or blade to just bevel the edge. 400F air expands >10x when heated to 750F and has to get out. If alloy cools on top of the air, you get wrinkles. If your venting is proper you want fast fill rate. Small sprue hole or nozzle will restrict flow. A problem ladle casting can solve, sometimes. 'Pressure pouring' is a misnomer. It can reduce 'heat' loss going into the mold but has nothing to do with pressure. Pressure is a function of height of a column of liquid and my pot is just as tall as your ladle.
    Whatever!

  4. #24
    Boolit Master daloper's Avatar
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    When I cast for my Ruger 480, I have to pour with a larger stream to get them to fill out. Open up the valve to pour faster.

  5. #25
    Boolit Master


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    If it's wrinkles, pressure casting should cure that. If it'd improper band fill out, the mould's too hot. This is a common occurrence with moulds with high capacity cavities. The solution there is to slow down the casting tempo and let the bullet cool. I have one mould that I have to cast, watch the sprue and when I see the sprue frost, I know it's cool enough and will make good bullets. Slows down production but unless you're making good bullets, you don't have production.
    The problem is that some moulds with big cavities have too much lead capacity and the blocks are too small in surface are to dissipate the heat between casts and run hot. This will cause incomplete fill out until you slow down the casting tempo.
    I have a casting table I used for a while when making 400 grain plus bullets. Had a squirrel cage fan mounted under a screen and blew upward. After I cast, I set the mould on top of the screen and waited for the sprue to frost. Improved production and my casting speed. Once in a while, a hardened drop of lead got through the 1/4" mesh into the fan and things got exciting for a couple of seconds. "Were you there when the sprue droplet hit the fan?" Anyway, that worked pretty good and these 110V fans can be salvaged from old computer chassis for free normally./beagle
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  6. #26
    Boolit Master



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    Quote Originally Posted by Winger Ed. View Post
    Raise the heat. In the alloy and the mold itself both.
    If you're casting something soft, add a little bump of tin the thin it out and improve the flow/fill out..

    To speed things along, (with a old bottom pour RCBS) I start out too hot.
    When I get solid frosting or 'fins', then I start easing back on the heat until they come out with just a small, little bit of frosting.
    ^^^^^^^ This! Get a $10 hotplate from Walgreens or somewhere and get the mold up to HOT, really helps on all my “monsters”
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  7. #27
    Boolit Master


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    Try pressure pouring with a ladle.

  8. #28
    Boolit Grand Master popper's Avatar
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    Try pressure pouring with a ladle. Physics says there is NO SUCH thing as PRESSURE POURING!!
    Whatever!

  9. #29
    Boolit Master
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    It's just a term people use to describe the process of pouring from a 'side spout' ladle with the spout held tight to the sprue hole or holding the sprue plate up against the spout of a bottom pour pot.

  10. #30
    Boolit Master


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    Quote Originally Posted by Hanzy4200 View Post
    It's a aluminum 2 cavity and I am using a bottom pour. The pressure casting is a good idea, I've not tried that. The issue with adding heat is that the mold is already over heating within 4-5 casts at the current settings. At that point bullets are getting extremely frosted.
    . This STILL dosnet mean that the MOLD is hot enough! Your allow may be too hot and the mold cold.

    Venting has been mentioned and it is an important part of casting a proper filled bullet. BUT its generally well done on current molds.

    Wrinkles are caused by the allow cooling BEFORE it flows completely. That can really ONLY happen when something is too cold.

    Someone else mentioned adding a bit of tin. This helps too as tin helps the lead flow. It usually dosent talk very much but usually isnt the case with COWW as these contain enough tin.

    Has this mold been seasoned? That helps too. But is NOT REQUIRED as long as your patient. Because simply using, (heating and cooling mold) is accomplished with use.

    If you mold is clean of any and all oils, made within the last ten or so years, (has proper venting) I STILL tell ya the problem is temperature.

    Good luck

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  11. #31
    Boolit Master


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    Quote Originally Posted by charlie b View Post
    It's just a term people use to describe the process of pouring from a 'side spout' ladle with the spout held tight to the sprue hole or holding the sprue plate up against the spout of a bottom pour pot.
    YES but the ladle dosent have the "HEAD" to creat pressure as a 20# pot will.
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  12. #32
    Boolit Master
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    I have no advice. This is the game we play. Without having your pot and your mold in my hands it's just a guess.

    Keep working on it, you'll figure it out.

  13. #33
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    Quote Originally Posted by Hanzy4200 View Post
    It's a aluminum 2 cavity and I am using a bottom pour. The pressure casting is a good idea, I've not tried that. The issue with adding heat is that the mold is already over heating within 4-5 casts at the current settings. At that point bullets are getting extremely frosted.
    Are you getting extremely frosted boolits that are wrinkly?
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  14. #34
    Boolit Grand Master popper's Avatar
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    Wrinkles are caused by the allow cooling BEFORE it flows completely. Sort of. If the alloy cools enough to trap air (and it doesn't take much 'air'), the increased air pressure will 'push' a wrinkle into the soft lead. Like a drop of water causing the tinsel fairy - high pressure/velocity gas takes some alloy with it when it vents. Tin reduces surface tension of the liquidus, antimony increases it and cools faster. OP didn't say what his alloy really is. Might need some As from shot (better surface tension). Impurities in the alloy can also cause wrinkles as they outgas when 'burned'. Tom must be using a flycut method for vents (economy) and they are not always in the right place. Lube grooves create a lip for trapping air as well as the alloy needing to flow 'under' the lip. I had a terrible time with one of his moulds, GC design and the last 'band' was terrible with fillout. I 'broke' the top edge and increased flow to solve the problem. Smoke the block faces and see if that helps. The tiny spacing between the halves might help venting.
    Whatever!

  15. #35
    Boolit Buddy
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    Pressure pouring/ casting is a partial misnomer as compared to the industrial scenario mentioned by Country Gent but as the term is used in this discussion it is still pressure pouring/casting. Any filling of a mold cavity as we do is to a degree pressure. What makes this so is that any time you hVe a quantity of liquid (known as a "head") above your outlet the pull of gravity on that "head" of liquid creates pressure. This is why you have water pressure at your faucet when water comes to you from a town water tower/tank. Three: things affect the amount of pressure at the outlet:
    1- the amount or weight of liquid,
    2 - the height from which it drops,
    3 - the size of the outlet.

    This is physics, hydraulics, etc. A 2lb pot has more head than a ladle because of more weight of liquid above the outlet/spout and a 20lb pot has multiple times the pressure at the spout. This is why casting changes as the alloy level in your bottom pour pot decreases. Less head =lower pressure. This is true with a casting ladle and is why you get better results when you try to fill the ladle the same each time.
    What is commonly referred to as pressure casting, as I have said, involves pressure but maybe is as much more direct fill and imitating the effects of sir in filling the cavity.

  16. #36
    Boolit Master Cap'n Morgan's Avatar
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    The pressure is determined by height and density (weight) of the fluid - volume doesn't matter as long as the height is the same. The amount of pressure is linear and doubles when the height doubles, meaning that a 5" lead-column in a bottom pour pot will deliver 5x the pressure compared to a ladle holding one inch of molten lead.
    Cap'n Morgan

  17. #37
    Boolit Grand Master Char-Gar's Avatar
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    Take a drill and enlarge the spru hole to get the hot metal in there fast. That will cure the problem.
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  18. #38
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    Quote Originally Posted by Char-Gar View Post
    Take a drill and enlarge the spru hole to get the hot metal in there fast. That will cure the problem.

    This is just not a real option for me. The larger the hole the harder it is to cut this effects wear and tear on the mold.

    Use this as last resort or order new spure and drill away. I really feel collectively we have solved the probelm if you can apply our suggestions.

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  19. #39
    Boolit Buddy
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    Ladle cast, you get much nicer bullets. I used to do the bottom pour, but as you are discovering the large bullets don't turn out well, I switched to full time ladle casting.

  20. #40
    Boolit Buddy
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    Quote Originally Posted by popper View Post
    Try pressure pouring with a ladle. Physics says there is NO SUCH thing as PRESSURE POURING!!
    Believe or disbelieve what you will. Pouring melted alloy from a ladle does not create MUCH pressure not does a 20# pot but pressure is created. It is the force of gravity acting on the wdight of liquid alloy forcing it through the bottom orifice that creates the pressure. If the weight of alloy is known the pressure or force may be calculated.
    I will agree that in this case the term "pressure casting" is at least partly misnomer as pressure is only part of what is in play. Speed of fill particularly with a drilled ladle spout but there is also the heat of the ladle or pot of alloy in contact with the mold. Then top it off with a fat puddle of metal onn top of the sprue plate and you're giving a big cavity the best chance at filling properly.

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