So, riddle me this.....
I have a MC that is automated, i have a fan to cool the mold down to give nice clean looking projectiles. The issue i get is after a few hundred drop out, lead builds up between the pivot point on the sprue cutter and mold. This pushes the cutter out a little and you get a bump on the back of the projectile. It's not nice and smooth after the BB, but a bevel then a raised bit. It adds variation to the weight and doesn't look as nice as where the lead picks up, it runs like a gouge on the back side too.
Now, the strange part.... If i don't turn the fan on and run it hot, this doesn't happen. Hot enough that the projectiles that fall are frosty, but have a nice even base. You can see lead build up on the mold surface, but it's very thin and doesn't cause any issues. I cast about 6,000 last saturday like this without any issues or needing to stop to scrape the lead off with a snap knife blade.
I can't use lube as i coat the case projectiles in polymer, so any oils are bad for making it stick.
I always thought keep it slow and cool and lead will not build up, but for me, all my molds build it up if i don't run them hot.
Has anyone else had issues like this? or is it just an aussie thing with our lead spinning the opposite direction? :P