Hey Doc,
I have been casting bullets for a very long time and I have tried so many different combinations of metals and metal temperatures and etc. Then I have tested the products in many various guns.
Your problem with wrinkling is one of two things. One is the mould is not up to temperature. The other is a lubricant place on the mould when it was in the factory. Let me tell you a story that I experienced this past Saturday with a new mould.
I bought a new Lyman 2 cavity steel mould. Now mind you, I own no less than 25 moulds from 10 Cavity Hensley and Gibbs to the Lyman, so I have had a bit of experience with new moulds. The Lyman instructions declared that if I used Denatured Alcohol to wipe off the protective coating on the mould, it would be ready in minutes. Or, I could use a spray parts cleaner, like brake cleaner that is readily available. After trying both of the prescribed methods the results were awful wrinkled bullets.
Totally frustrated, I resorted to the best way to clean a mould. I mix a 50-50 mix of TSP & Spic n Span and put one tablespoon of the mix in a pan tall enough to keep the mould under water and then boil the water with the mould for about 15 minutes. Remove the mould, rince it off with clear water, dry and set aside until completely dry. I put my mould pieces on the stove with a flame under them and the dried in a hury.
Now the mould is ready for some serious casting. In order to get you mould up to temperature quickly, pre-heat the mould on the stove, preferably on an electric stove. I have a small electric hot plate for this.
Now, you first few casts will not be up to standards, but they will start filling out without wrinkles very quickly. Frosted bullets work just fine and they are usually the best filled out of all.
My new Lyman mould gave me fits until I boiled it. I have boiled all my moulds for 20 years and it works.
However, the only aluminum mould I have is an LBT (Lead Bulet Technology) 4 cavity and I find that aluminum big block moulds are harder to keep up to temperature. If it is not kept in action at a steady pace, it will start to wrinkle from being too cold.
When I cast, I always use 3 moulds at the same time. When using the aluminum mould, I can only use two moulds so that I can keep the aluminum up to temperature.
I have used wheelweights as my base metal for many years. Adding 2 or 3% tin, which can be purchased as pure tin, and the bullets fill out much better at lower temperatures.
I have used lead shot, recovered bullet lead, sheets of lead and I mix it with Tin and sometimes linotype.
Currently, I have been using wheelweights with 2% tin. I also, have been using 3 pounds of wheelweights to 1 pound of linotype. I think the ww+2% metal shoots better in my rifles and TC Encore handguns.