Bulseyetom wrote on Apr 2^nd, 2020 at 7:58pm:


I cast both 20/1 and 30/1 at 775 degrees (according to a Lyman thermometer) and cut the sprue as soon as it solidifies.  This works for me on everything from 118 grain 25 caliber bullets up to 535 grain .45 creedmores.

JackHughs

Tom, I would start at about 775.  After about 20 bullets they should be consistent weight and well filled out.  If they are not, go hotter.   

I watch the sprue puddle harden, wait a few seconds, then cut it off. 

If the melt is to hot, the mold will take too long to cool and the sprue will be slow to harden.   If the mold is too hot, leave it open for a few seconds.  It will cool 10 times faster open than closed. 

If the melt or mold is too cold, you won't get good fill out.

The trick is to find the temp that make good consistent bullet at a comfortable pace. 

I run my temp a fuzz high using a thermocouple on my mold. Occasionally, I have to wait about 20 or 30 seconds for it to cool.  If the gets 10 degrees low I either poke the mold in the pot to get it back up or  pick up the pace casting as fast as I can to get it back up.   

With the thermocouple on the mold, 90% of my 215 gr bullets will be +/- .1 gr.  Without it, +/- .3 or .4 with a few .5. 
 
If the mold it a little too hot, it won't matter much, but will slow you down waiting for the sprue to harden.  If it is 10 degrees too cool, your weights will start to vary a little. If you see flaws, it is way too cold.

Good luck     

The one thing that improved my bullets more than anything else was drilling and taping the corner of the mold to attach the thermocouple.

I agree the sprue plate temperature is critical to a good cast bullet. I fill/puddle the top of the plate on every pour to the point of almost overflowing. By doing so I get full filled sharp base bands. If any of the custom mold makers are watching an option to countersink a sprue plate leaving a slight lip around the perimeter to help contain the puddle would be a selling point for me.

I personally prefer using brass and I have found it requires a bit higher casting temp. So I cast at 800 or 800+ and cut the sprue as soon as it freezes and then continue to cast as fast as I can.

I puddle enough lead on the sprue plate so that it runs off and forms a tail that hardens. My solidified sprue rarely drops off when I cut the sprue so I grab this tail to pull thislead off the sprue and return it to the pot.

I might also add I recently cut a 35 bullet mould for a 35-40 for a friend. I then cast a bunch of bullets to make sure the size turned out right, it was cut well centered, the bullets were round and they dropped right out. My bullets weighed 277 grains with 1-16 and when he cast his own with 1-20 they were not even close to being the same by allot and more than the differing shrinkage rate. We're they still round, the correct size and did they still drop right out. That I don't know with the difference being that much nor do I know how that could be. The point being we all tend to cast very differently and it,s highly likely that our results are ever quite the same. It can also complicate how much to oversize your own cherrie's to actually get the correct size that you want.

John,
I really like what you did to those mold handles. 
the setscrews to keep the blocks straight into each other
rather than wobbling on the block pins.
beltfed/arnie