RCBS 30-180 FN newer mould question

[45&30-30]

I sat down today and got a good measurement on 10 bullets I cast a few days ago. WW, WC. They are .305 to.307. On the seam line they can go as high as .308. I have been considering lots of options I have found on the forum. I am waiting on the pot to warm up right now. I will be adding tin to a 20 pound pot of WW's. Not sure how much to add, but I want to see if this will fill the mould out better and get me to .309 or is this just going to be a waist of time. Should I talk to RCBS about sending it back? Thanks for anyone who can help.

Edit, that should be air cooled not water cooled on the WW's. Thanks

[rvpilot76]

Don't measure on the seam line...

[45&30-30]

I didn't word that very well, the first measurements were for the rest of the boolit body and the last measurement was up to .308 on the seam line. Sorry for the confusion.

Edit- One more question I casted the bullets with the auto body filler, 40/60 tin/lead and there is this bright gold, blue and purple colored film that rises to the top and it clings to the ladle. I added about 2 inches of this from a 1/4" by 1/4" by 12" square stick. Any ideas what this could be.