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Thread: Brass Mold Help

  1. #1
    Boolit Buddy
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    Brass Mold Help

    So I recently purchased a 4 cavity 9mm hollow point (with all the extra pins, also no lube groove) from MP Molds. So I take it out of the box clean it real good and install the penta pins and used the provided lube. I cast around 40, then let the mold cool off and did that 3 times. This is where my problem starts, I fired up the pot today to cast some hollow points. I can not get them to come out without wrinkles, and the bases are not properly formed either. No matter what I do, I have yet to cast one good boolit with this mold. I know I'm doing something wrong, this is my first brass mold, I'm just looking for some help. I'm going to work now and will be home at 10 to reply back to any questions you may have for me. Thanks in advance for any help.

  2. #2
    Boolit Master


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    My mp brass hp molds like to be run hot, as hot as I can make them and the first 3 or 4 pours usually go back in the pot. If you did your prep right which it sounds like you did it's probably mold not up to temp issue, you didn't say anything about your alloy could be it could use a little tin but again I don't know what your using,I've found no matter mold material sloppy bases and wrinkles are from to cool galena /mold temp.

  3. #3
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    Also make sure there is no oil in the cavities. You can get it from the pin lube migrating into the cavities. I use dry moly on those alignment pins that hold the HP pins. The mold block alignment pins too.

  4. #4
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    Brass Mold Help

    To start you didn't properly heat cycle it. You want to cycle it in an oven at 400 for an hour, let cool and repeat three times. This builds a patina. Luckily you didn't say the bullets are sticking because this is usually what happens when you don't build the patina first.

    Your problem is the mold isn't hot enough. Preheat it on a hot plate to full casting temp. W/ a brass mold this is pretty much a necessity. Turn up the lead temp if you have to. The minimum I use for a brass mold is 725. There are plenty of times I've gone north of 750. You need to keep the mold blocks and pins hot if you want perfect bullets. So get the mold hotter and you should be good to go. If you have to cast faster w/ larger sprues do so until it drops perfect bullets.

    Edit:
    The heat cycle I described is my preferred method. If you're using an alloy w/ any tin in it you run the risk of tinning a mold if there is no patina. I know about this first hand and it's no fun to remove.
    Last edited by dragon813gt; 07-31-2017 at 07:47 PM.

  5. #5
    Boolit Mold
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    dragon813gt pretty much summed it up. When I first started casting i was having the same problems until I increase my lead temperature to 725 and preheated my molds. I also want to mention to make sure you preheat the sprue plate as well.

  6. #6
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    I contacted mp molds and did exactly what they said to do as far as breaking the mold in. My boolits aren't sticking and the mold does have a petina to it. I think I'm good there. It has to be a temp problem. I'm using 19 lbs WW lead with 1lb Linotype added. Boolits fill out nicely in my other molds but the are aluminum. I don't own a hot plate, it is on my list of stuff to pick up. Can I heat the mold by putting the corner of the mold in the lead? Thanks for the replies.

  7. #7
    Boolit Bub AnotherNew1's Avatar
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    I too will be using a MP Mold soon enough. I have no input but will be watching and waiting to see HawgFan's Corrective action. Please keep us updated HawgFan.
    Thanks
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  8. #8
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    You want a hot plate w/ brass molds. You can dip the corner but that's not gonna do much. As I said the mold and the pins needs to be hot to cast perfect bullets.

  9. #9
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    I often heat my MP brass molds by just sitting them on the edge of the pot. However, I also then heat the sprue plate and pins with a propane torch. Takes some trial and error to get things just right. I have also heated my molds with them sitting on the electric range. Beware, keep it low until you get the hang of it. I have one mold where it looks like it is beginning to crack and shows a heavy copper color.

    Pins
    I take every one of my pins and polish them with 600 grit wet-dry sandpaper. Most of the blueing is gone. Then I warm them and apply Dri-Slide. It is molybdenum disulfide in alcohol and something that makes it stick until the alcohol evaporates. You can use this on the bottom side of the sprue plate too.
    http://cdn.shopify.com/s/files/1/009...634b32d.pdf?78

    Alloy
    Try without the lino. For most applications clip on WW are good. I usually cut mine 50/50 with scrap lead. Work fine even in full bore loads for .30-30. 44 mag no problem.

    Temperature
    I tend to cast at a lower temperature than most. However, when I get going I keep it moving to keep that mold and pins up to temperature. And, I ladle cast with a lot of lead spilling over the sprue plate back into the pot. Just how it seems to work for me. YMMV.

  10. #10
    Boolit Buddy
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    I think I finally got it working. I set the mold on top of the pot while the lead was melting, then I stuck the sprue plate in the lead for about 2 minutes. After about 4 bad casts everything started to look great. My mold was hot enough that it took a 5 second count for it to harden. Thanks for all the advise.

  11. #11
    Boolit Master

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    My pre-heat method is to sit the brass molds on a piece of 3/16" steel plate on a hot plate and heat until the sprue plate lube just starts to smoke which is a bit too hot. The sprue will take a few seconds to freeze but settles in pretty quick as the mould cools a bit while I cast.

    Longbow

  12. #12
    Boolit Buddy
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    Quote Originally Posted by dragon813gt View Post
    You want a hot plate w/ brass molds. You can dip the corner but that's not gonna do much. As I said the mold and the pins needs to be hot to cast perfect bullets.
    Disagree with ya dragon - we cast with several CBE brass molds (44/40,38/55,348,) - just dunk the corner in the lead - that brass heats up quick and when its hot enough it dont stick any solid lead when ya take it out - its ready to go. I dipper cast from a 20pound cast iron pot - over a gas ring - always make sure I get a fresh dipper of hot stuff from deep in the pot - you wouldnt think that make any difference but it does (a lot of difference)

  13. #13
    Boolit Master

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    If it cast good bullets during the break in with this alloy and temp then something has changed in the mould. Try cleaning the vent lines out on each half with a bamboo skewer sticks fine point. Also try a soap and water cleaning before casting each time. My brass moulds are Old West made by Bernie Roweles. My procedure is as follows the night before I give them a good cleaning with dawn dish soap and hot water scrubbing with a toothbrush, I lather up 2 times then rinse completely. let dry a little A blow drier will speed this process. I then lube with 2 cycle synthetic motor oil. the next day when I fire my pot up I set them on a rack beside the pot where the flames leak out to pre heat. ( I normally run 2 2cavities at a time) When the lead is up to temp I start casting with them alternating as I pour. I normally get good bullets from the start this way. I run around 725* on the pot and ladle cast at a fairly brisk pace.
    You can dunk the front lower corner of the front edge in and hold when lead no longer sticks it should be close to running good. Run hot enough that it takes a few seconds for the sprue to "frost" over. You will know this when you see it. As to the alloy ww and linotype should cast good a1% or so of tin may help flow and fill out a lot also. Probably not needed if the mould did cast good bullets before though. Another thing to do is pour a large sprue ( to the point some runs off the edge) this helps keep the sprue plate hot and also allows gasses to vent more. My first guess is there is some build up plugging a vent line off and restricting the air being pushed out.

  14. #14
    Boolit Master Harter66's Avatar
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    I have a 2 cavity 462-420 with HB and plain base pins .
    I did the wash , heat cycle , assembled ,heat cycle ,lubed hot , cooled , heat cycled , cooled , pre heat (cast iron kettle plate on an open coil hot plate) , pour 20-30 pours , cool reject whole run , preheat pour 20-25 , wash hot mould with brake clean , reheat pour some more rejects ........... 12 cycles and then as if my some magic a 20% reject , 80% keepers . All the keepers are within .5% weigh lot and only a few outside of a .3 gr over/under .

    It took 12 full cool , full heat 8 were complete cool preheat casting cycles . 12 cycles . In my little slice of heaven things don't rust and brass barely dulls in under 5-6 yr . It took 12 cycles over a couple of weeks , 12 cycles .
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  15. #15
    Boolit Master
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    Cast hot, cast fast, and look the world right in the eye.

  16. #16
    Boolit Master
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    sounds like you aint near hot enough
    either the mold or yer lead
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  17. #17
    Boolit Master Forrest r's Avatar
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    Odd, I own around 20 brass molds and have never "heat cycled" them when new to get a break-in/patina. Never had a problem.

    I've used a hotplate for decades to heat molds, had a lot of the big steel 6/8/10-cavity molds and that was the best way to get/keep them hot. The old hotplate I was using finely quit working so I bought a new 1 at walmart for $20, bought this 1:
    https://www.walmart.com/ip/BLACK-DEC...1001B/21582291

    It has a dial/heat settings that go from 1 to 6. I turn it to 5 and start heating the molds when I turn on the #20 pot and start filling it. I run the #20 pot at 725* when casting with hp/hb molds. As others have stated the molds will start to smoke when they get hot. By the time the mold starts smoking the #20 pot is ready, time to cast.

    The 1st pour is always hot & the sprue's take awhile to turn solid. That's telling me the pins are hot enough and the bullets fall out of the mold and are frosted. From there it pour another round and wait, dump, let the mold stay open for 10/15 seconds and do another set. It doesn't take long for the mold to cool down to where you have a sweet spot for your style/speed/cadence of casting. The 725* alloy temp aids in keeping the pins hot/casting god bullets. Doing the hotplate/725* heating of the alloy/molds and then settling into a cadence produces good quality bullets that easily fall out of the molds and are just starting to frost. Some mihec 359640's that are starting to frost from a 4-cavity mold.
    [IMG][/IMG]

    Some mihec 432256's that are frosted from a 4-cavity mold.
    [IMG][/IMG]

    Some mihec 452200's that are frosted from a 4-cavity mold
    [IMG][/IMG]

    Some mihec 9mm-125's that are frosted from a 4-cavity mold
    [IMG][/IMG]

    Doesn't matter if I use a 2-cavity or a 4-cavity mold with the cramer pins. Doesn't matter if I use brass or steel molds. I use the same heat setting and get good bullets from the 1st pour. I also use the same heat setting when casting with lyman/h&g molds that have hp/hb pins along with the raphine molds with the hb pins.

    If I'm casting with al/steel/brass molds that don't have pins I turn the alloy/#20 pot down to 700*. It's a personal preference, when I cast bullets I like to cast them with the mold/alloy hot enough so that I see that the bullets are just starting to frost. When I do that I get good bullets from the 1st pour, have excellent fill out and more importantly. If the bullets start coming out shinny/not frosted (cooling down) it tells me I either need to go faster or turn the alloy temp up. If I see the bullets are coming out completely frosted like the 432256 bullets pictured above, (getting too hot) it's telling me to either slow down or turn the alloy down.

    The other thing I don't do is toss the sprue's back into the pot when I casting. I let the pot heat cycle itself without adding cold/cool alloy into it.

    I highly recommend you get a hotplate, just makes casting easier. It's nothing to heat heat 2/3/4/5 different molds and work them in during a casting session. I do this when I cast rifle bullets from the single cavity molds that I have or when I'm casting with a regular mold and want to cast some single cavity hb/hp bullets.

    Frosted bullets never bothered me & I find frosted bullets coat lot better/easier when pc'ing them.

    just another opinion, good luck & enjoy your mold

  18. #18
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    Ignore your boolits as you cast and keep the temperature up. Brass molds seem to take longer to heat up than do Iron or especially aluminum molds. Stopping to peer at how you are doing allows the mold to chill and lengthens the time it takes to get the mold hot enough to cast those sweet keepers that you are searching for. Provided your melt is good--no zincers in it--and you pre-heat the mold. either on a hot plate or on the top of your furnace as the melt comes up to temperature, you'll get good boolits quickly.

    IME those Penta-points are the hardest to get to cast good boolilts.
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  19. #19
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    Quote Originally Posted by rintinglen View Post
    IME those Penta-points are the hardest to get to cast good boolilts.
    I always polish mine up with fine wet-dry sandpaper. And, I smoke the points. Really makes a difference.

  20. #20
    Boolit Master stubert's Avatar
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    I have a NOE 5 cav. that likes 450 deg. using the temperture probe.

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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
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