Hollow Base Mold Update

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  • Last Post 19 April 2016
cove posted this 12 April 2016

A while back I asked for opinions on casting techniques using a 148 grain HBWC mold.  I was having trouble getting the base filled out with sharp edges and the bullet sticking to the pin.  After numerous unsuccessful attempts, I tried the obvious, turn up the heat.  I normally cast at 750F and avoid higher temps in an effort to keep the alloy from oxidizing.  Info included with a Lyman thermometer says to cast wheel weight alloy at 600F.  Well I don't think that's hot enough since I started getting good bases and release when the temp was turned up 825F as confirmed by 2 thermometers.  I guess the more complex cavity due to the pin requires a more fluid alloy to fill the narrow skirt.  Of course the higher temp requires more fluxing and oxide loss. Never too old to learn new tricks-Cove  

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Ed Harris posted this 12 April 2016

What alloy are you using?

I never had any trouble casting #575213-OS at 750 using 1:40 tin-lead from a botom-pour pot with crushed clay kitty litter over the melt surface.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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OU812 posted this 13 April 2016

Maybe your mold was not hot enough. Dip the end of mold and sprue plate in melt to preheat. About 25-30 seconds should get mold hot enough or maybe too hot. I would rather start casting with a mold that is too hot any way.

Sometimes I have to turn the melt temp up to 850-900 to get good bullets...especially 22 caliber. Wheel weights, Birdshot alloy etc has no tin, so you do not have to worry about tin burning off. A little Antimony and more heat does a great job at filling out mould. 

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Brodie posted this 13 April 2016

If you are getting poor fill out on the skirt of the HB mould try dipping the pin into the melted alloy for 20 to 30 seconds.  A lot of time the pin does not keep up with the mould as they heat up.  If the pin is too cold the skirt won't fill out completely. Brodie

B.E.Brickey

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358156hp posted this 13 April 2016

Brodies right. The pin loses heat quicker than the mould does, and unless you heat it by other means it will remain at a lower temp than the mould blocks will. This usually shows up as an incompletely filled skirt. Some guys dip them in the melted alloy while dropping the bullets from the mould, some guys heat them with a small torch before reinserting (assuming you're using a Lyman mould). If you are using a mould with captive HB pins, like a Cramer or NOE, you really need to look into using a hot plate to keep everything at the necessary temperature.

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delmarskid1 posted this 15 April 2016

A hot plate with a stove lid or other thick piece of metal over it is a nice way to keep a mold warm. I used to heat the forming pin with a bottle torch until things got rolling.

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358156hp posted this 15 April 2016

In cold weather I've gone as far as to make a holder out of coat hanger wire that held the hollowbase or hollowpoint stem in the molten alloy. That really made everything better in my unheated garage.

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cove posted this 19 April 2016

Thanks for the input guys.  The mold is an aluminum N.O.E 360 148 HBWC and my normal allow is 30-1, but I tried wheelweight with the same results.  I borrowed a bottom pour pot and after a lot of experimentation found I could get bullets that were filled out by holding the sprue hole in contact with the spout so the lead is pressurized by contents of the pot.  I also modified one of the pins so it was more rounded, similar to the pin in Lyman HBWC molds.  As mentioned above, I have to keep the lead at 800 degrees and cast quickly to keep every thing hot and am still having success using a sprue wrench as I described in an earlier FS.  The sprue is cut immediately after it frosts with a very slow cutting motion.  The less than perfect WCs I cast last summer shot well out to 75 yards and I'm optimistic that the well filled out bullets I'm getting now will shoot as well or better. All I need now is for the weather to straighten up. Thanks again -Bill Duncan (Cove)

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