Lyman/Thompson mold

[mdi]

I just finished casting a couple hunnert Lyman 429244 with 50% stick-on ww, and 50% clip-on ww, air cooled. As I was measuring them I discovered the front (top) driving band was .002" smaller than the other two bands (.430"-.431" vs .432"-.433"). I don't remember this difference in the bands the last time I used this mold 3-4 years ago (but how can a mold change in a few years!). Is this just the Thompson design? Or did I get an odd ball mold? It's a single cavity mold of undetermined age (old).

[Shuz]

I have an old Ideal 429244 SC mould that also casts smaller on the FDB than the rest of the boolit. However, mine is more pronounced in that the FDB is .425-.426, and the others are .431-.432.

I have another SC 429244 that is a Lyman that has been hollow pointed and scalped to remove the gas check shank to give an end weight of 222g and all driving bands are .433-.434 to start and finish up real nice at .431 or .432 depending on the H&I die used.

Perhaps the difference in FDB's depends on whether it is a Lyman 429244 or an Ideal 429244?

[runfiverun]

i wouldn't worry about it too much but i would look for a little ding on the upper half of the mold,
or on the top half of a cavity.

[Mal Paso]

I had 2, 4 cavity Lyman 429421 molds that had a small front drive band but tapered to a larger but undersized rear band. I lapped one of them to .432+ on all bands.