Bullets Won’t Release From Mold

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I have 2 NOE brass molds.  The first is a 4-cavity, PB, 360-160-SWC that won’t let go of the bullets.  It takes so long tapping on the hinge bolt that the mold has cooled down 30 degrees before all four bullets have dropped.  The second is a 2-cavity, PB, 360-160-WFN that drops the bullets after one or two taps on the hinge bolt.  I am running the pot at 700 degrees using both molds with the same alloy batch.  The molds are both run at 400 degrees.  Both molds turn out beautiful bullets.  The sticky mold has cast about 1200 bullets.  The one that they fall out of has about 200 bullets cast.  While I have a lot of experience improving Lee molds, I am not about to make any changes to one of Swede’s molds.  Any help would be appreciated.

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[robertpedersen1]

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400 F is generally too hot for a brass mold.  (I haven’t tried NOE’s brass molds, so that statement is based on other brands.)
It’s probably warping with the heat, and distorting the cavities to the point that they ‘pinch’ the bullets.

Check the mold while it’s cool.  Look for gaps between the blocks, due to the blocks bowing inward and closing the cavities slightly.  (More metal on the outside, pushing the cavities shut, due to thermal expansion when heated.)
With some molds from other manufacturers, brass molds come warped, right out of the box.  It’s due to lack of stress relief for the blocks before cutting the cavities.  (Much more pronounced the bigger the cavity.)

[johnkierParticipant]

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Thanks for the input Squigie.

No warping was evident when I checked 24 hours after using the molds.  There is no light visible between the mold blocks.

When the molds were new I ran each through five cycles up to 350 degrees and back to room temperature to break them in.  Then I started casting with the alloy at 700 degrees and the molds at 320 degrees.  The bullets were wrinkled, so I increased the mold temperature 5 degrees each three casts until the bullets came out smooth and completely filled out.  That was 420 degrees for each mold.  After a few casting sessions I have been able to drop the mold temperature five degrees at a time and keep casting good bullets.  I am down to 375 degrees on the 4- cavity and 400 degrees on the 2-cavity.

[adamsutherlandModerator]

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I would contact Al direct.

It does seem very hot mould temp, when you were getting the wrinkled bullets did you heat up the sprue plate before the mould to see if that was the problem first. Hot moulds can still have cold sprue plates that will cause the alloy to cool, a hot mould does not always guarantee a hot sprue plate.

Also the design of this mould looks as though it would be prone to hanging up as well.

[johnkierParticipant]

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Thanks for your help dromia.

I have a tendency to miss the forest because I am looking too intently at one of the trees.  The thought of a cold sprue plate causing me to have wrinkled bullets at lower temperatures never occurred.  I have been setting the mold on a hot plate until the temperature reaches my target temperature and then beginning casting.  Since the temperature probe is in the bottom of the mold it makes sense that the sprue plate would be much cooler.  I’m going to bend a metal box to fit over the hot plate to act more like an oven and leave the mold in much longer for the temperature to equalize over the entire mold and the sprue plate in the future.

I wondered about the bullet design contributing to my release problem too.

I will see what Al says.

[tylercroweParticipant]

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I have very limited experience with brass, but I have 7 or so NOE aluminum molds and I’ve found they all like being run about 425*F.

[Hugh KuhnsParticipant]

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This isn’t my idea but I tried it and it works for me… I use an electrical junction box that is 4 or 5 inches square and cut a hole on one side to slide the mould into it. Place on top of the hot plate and surround the mould and hot plate with fire brick to make an oven and hold the heat inside. I cover the top with short pieces of lumber to complete the oven. This will bring the temp up to 400 in 10 minutes or so. If you have a mould with temp probe you can monitor without removing mold to check it. I also have installed a thermometer from a BBQ grill on top of the junction box. Buy  this at Home Depot in grill parts section.

762sultan

[Full.Lead.TacoKeymaster]

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I have very limited experience with brass, but I have 7 or so NOE aluminum molds and I’ve found they all like being run about 425*F.

My aluminum ones also like to be run around that same temperature, but the brass ones a bit cooler.  You do have to watch out as to not overheat the brass molds because it seems brass is more prone to warp than the aluminum.  I know some people don’t like to smoke their molds, but have you tried putting a little smoke inside the cavities?

[Author]

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