Uneven frosting w/ Lee molds?

[yondering]

I've found that my boolits cast from Lee molds often have uneven frosting on one side, usually at or near the driving bands, and centered in one mold block (not near the vent lines, but in the center of the cavity). This causes an uneven boolit, the frosted part is visibly shrunken. Shrunken driving bands on one side is obviously not conducive to best accuracy, so it's pretty annoying.

I noticed last night that this always seems to happen on the left block, the one with the sprue plate attached. It seems maybe this is due to heat transferred from the sprue plate to that block. My fix, while casting last night with my Lee 452-300-RF two cavity mold, was to briefly quench the left mold block in a bucket of water every other cast. I was dipping it in just enough to wet the base, not dunking it. This seemed to work well, nice shiny boolits that were well filled out. This was with straight wheel weight alloy, at 750 deg F.

Have any of you guys run into this, and what was your solution?

[docone31]

Yeah, I had that happen on one of my Lee Molds.
What I do instead, is to let the castings sit in the mold just a little longer than I usually do. Once the sprue plate goes up in temp, I get even frosting.
With those Lee Molds, the sprue plate has to come up to temp also, otherwise, it acts like an heat sink.
It does show up.

[tactikel]

I had the exact same observation last casting session, didn't know what to make of it!- Thanks for the solution. :drinks:

[fredj338]

I have seen this happen too. Thanks for the thought. I don't know about dunking them in water but a damp rag or large alum. block heat sink maybe.

[GabbyM]

It's the 300 grain 45 caliber boolit that's the culprit. Simply a ton of BTU's. Don't think it would make much difference what brand of mold. I've had a couple double cavity 264 grain 375 rifle molds that were hard to get round bullets from. Both iron blocks. My 405 grain 45 caliber rifle mold is a single cavity and works better. If it over heats it's all the way around the bullet. You're on the right track with a cooling routine. A small fan blowing across your dropped bullets then your mold will help cool the blocks. After opening the mold hold it in front of the fan for 4 seconds.
Two mods in rotation works well for people who like to keep moving.

[yondering]

It's the 300 grain 45 caliber boolit that's the culprit. Simply a ton of BTU's.

Sort of; although I have the same problem with six cavity 40-175-TC and 45-230-1R molds, as well as a 2 cavity 45-230-TC and a .309 200gr single cavity. All lee molds, none of my others do this.

[chevyiron420]

i have the same problem with my little 100 grain 32 mold. it will get so bad that ill start losing the driving bands in one spot wile the other side is fine. your right it always on the side with the spru plate. it seems i have to do a balancing act between to cold and fill out problems and too hot with bad frosting in one spot. my reject rate with this mold is terrible. i have other lee molds that dont do it.

[Andrew Quigley]

Goatlips has a website that has good info for dealing with Lee molds and lots of casting. I followed his advice to use a wet rag to cool the sprue plate. Once everything is up to temp and I start to get a little frosting I lay the sprue plate on the wet rag for a few questions and then dump the bullets. Doing this lets me cast for quite awhile with any of my molds from .380 up to my 45-70.