I just bought a couple of antique 38-55 rifles, and set up to cast for them. I have had a couple of modern rifles in this cal and have cast for them without any problems. My old Lyman Mag 20 pot quit working and I bought a new RCBS pot and a couple of new molds--an NOE 385 and a lee 365. I mixed a 1-30 alloy of 5 lbs new Rotometal 1-30 nuggets and a 5lb mixture of x-ray room lead and 30-70 bar solder. I have used the x-ray lead and the bar solder many times with no problems.
I prepped the molds exactly according to the instructions which came with them--cleaned the NOE mold 3 times with toothbrush and mean green soap, and heated it in the oven to 350 deg 4 times. Used denatured alcohol and a toothbrush on the Lee mold. Smoked them and put small amount of beeswax on the hinges and pins, Set the pot at 700 degrees and started casting. Even after about 25-30 bullets in the mold which had been heated on thetop of the pot. Bullets wrinkled. Tried cleaning both mold cavities with denatured alcohol a couple more times, and turned the pot up to 800 deg. Bullets wrinkled. Turned the pot up to max-850 deg, and recleaned with denatured alcohol, resmoked. I used paper matches, wooden matches and Bic lighter to smoke the molds.
Even with the pot up to max, temp checked with a thermometer. no frosting and wrinkled bullets. I have been casting bullets for 40 years and I never had this problem. I don't think there is any way I got contaminated alloy, unless it came that way from rotometal. I have used aluminum molds from Lee and Accurate and gotten good bullets. What am I doing wrong?