I never thought I had trouble with the 358429, cast and shot thousands with an old single cavity Lyman. Until I started shooting longer range regularly. I started a thread here a while back about it, they shoot fine until I stretch it out to 75 yards or more. Then I get really erratic flyers, like 2’ off in any direction flyers. I haven’t really tried to sort it out yet, I’ve been busy and it’s been hot. But I did buy a 38-150KT RCBS mold as one possible solution. I’ll start casting more this fall when it cools down a little and maybe get to the bottom of it, or maybe just go with the RCBS.
Flyers at longer ranges usually reveal a flaw in the mould or in the sizing process. Sometimes it can be in the casting process if the mould and alloy aren't at the right temp.
If sizing base first, especially with a Keith design, you won't detect misalignment very easily, whether dropping from the mould or after the sizing process, and if its in the mould at the nose, a runout gauge is the best way to find if its an issue.
Bullets with long, unsupported noses that are unconcentric basically create a yaw that rifling can only hide briefly, but the same ones that are concentric will be ballistically superior and often much more accurate at long range over more blunt or lighter weight designs.
