Mold Temperature

[Chris C]

I've got a mold that I'm finding 740* lead seems to work best with. When I'm running smoothly, my mold temperature is between 425* and 433*. When I preheat my mold, would it make sense to preheat to a much higher temperature and let it settle as I start molding.................or should I just preheat to about 450* and start? The reason I ask is yesterday I preheated the mold to 575* and it "seemed" as if the bullets weren't quite right until the mold settled down to the 425-433 range. If I'd had someone sitting beside me weighing them, I could have verified that, but I couldn't do that and keep my casting cadence at the same time. I'm only guessing, but it felt like the first 20 or 25 bullets should have gone back in the sprue box.

[Randy C]

I don't have a digital gauge to check mould temp but I think it depends on the combination you use it may change depending on the mould and alloy you use. I didn't answer your question, but it would be nice to start in the sweet spot.

[OS OK]

I preheat on a 1,500 watt unit with the skill saw blade on the elements (thermostat is adjusted 1/2 way to hot)...my mold temp yesterday was again at 429*F. and casting pure lead at 700* I got keepers literally on the first opening.
Not using a PID on the pot, the lead will drop back towards 625* as I adjust the thermostat down and put sprue cuts back in the pot and my weight variance on the last batch of .38/.357 HP's was 3 grains max on a 160 grain mold.
Had a total of 2 with incomplete bases out of 80 I casted...that was my fault for going too fast.

[country gent]

I would pre heat to 425* maybe even 400* then let the lead bring it up. If you heat it over where it wants to run it will take longer to solidify the bullets, Frosting may be an issue, and fill may be affected. Starting a little on the lowside ( around 400*) allows the mould to normalize right where it wants to be and should make good bullets from the start or maybe one or two fills to normalize it.

[Sur-shot]

Chris,
If this helps, I preheat my moulds by sitting them on the edge of the casting alloy, using 4 iron moulds at one time. The number of moulds at four seems to keep the moulds at a constant temperature and allows them to cool down so they throw proper bullets constantly. I use a RCBS Pro Pot and mostly RCBS or Lyman moulds.
Ed

[Chris C]

I would pre heat to 425* maybe even 400* then let the lead bring it up. If you heat it over where it wants to run it will take longer to solidify the bullets, Frosting may be an issue, and fill may be affected. Starting a little on the lowside ( around 400*) allows the mould to normalize right where it wants to be and should make good bullets from the start or maybe one or two fills to normalize it.


Followed your advice today and things improved. Not only did pre-heating the mold to 400* alleviate the initial 15 or 20 bad bullets waiting for the mold to stabilize, but my curve was much more consistent. (Though I'm far from "there" yet!) Thanks for the suggestion.

[runfiverun]

ahhh aluminum...
se post number-4.
toss everything until it's right then go on and make a pile of boolits.
when it's right is when the mold is at the right temp [dumping boolits easily]
only you won't have to mess about measuring it, you'll know when it gets there.