I use the Lee push through sizer and it helps cut back the diameter to the right size. Try the .355 for 9mm and the .356 for the .357. I didn't size the bullets the first few castings to see how consistant the mold was, and was getting leading in the barrel too. Now, I fire up a pie pan full of 3 parts Canning Wax, 1 part petroleum jelly, and a tube of Lee Liquid Alox. I actually dip the bullets in the wax with a pair of needle nose to cut down on the extra lube wasted on the cone. I let the waxes cool and then push them through the lee sizing die. You might try the different sizes though, it will help with the seating and the rest of the semi auto problems.
For the .357, sounds like the bullet is actually fitting in the barrel with the tumble lube covering the whole bullet. Most people use gas checks on the .357 too, it cuts alot of the lead out when sizing the bullet and such. It's not velocity, but size of lead. There should be enough antimony and tin in the lead from the tire weights. You could add an ounce of tin solder per pound of lead and keep the heat up to keep it mixed. You might also try fluxing the mix when you're casting it, with some bees wax. But, the actual bullet size is what makes it lead out the barrel on the 9mm.
