I had an experience with a Lyman DC .400 mould I bought. One cavity cast .400" x .400" while the other cavity cast .392" x .400".
I tested those oblong balls against the round ones from my Lyman .395" mould, that actually cast .398"x.398", in a proven rifle with it's accuracy charge.
I shot them from the bench, using an adjustable Bench Rest and sand bag rear, as well as standing. That Goodoien barrel has a .398" bore.
The results were rather dramatic. Oft times we have seen, in print, the load doesn't matter because I shoot offhand only. Well, if a load isn't accurate from the bench,
that inaccuracy is compounded when shot offhand, as shown below.
Just thinking out loud, I should never have sold that rifle.