I own a Lyman 429421 two cavity and a 429421 four cavity mold. They both cast beautiful bullets that come out at between .431 and .432. I also own two S&W Model 29s whose cylinder throats both measure .4335.
I made a .003 shim for my four cavity mold that causes it to create out of round bullets that measure around .435. When I lubricate and size these using my Lyman 450 and a Buffalo Arms .433 sizing die I get round .433 bullets.
This is not a very elegant solution. The shims do not last very long. Lyman just told me that they do not offer custom molds and they recommended RCBS.
Have any of you ever faced this challenge? What suggestions do you have?