run out question

[bruce moulds]

chaney,
don't panic. it takes a bit of thinking and having a go to come to grips with.
i only mentioned it on reading that you had gone to the trouble of getting a runout gauge, suggesting that you were really into runout.
holding them and squeezing them and reading the wind are much more pressing issues.
when you light the fire, the first thing that happens is that the bullet bumps up to whatever space it is in.
if this happens to be off centre, out of line, or reverse taper, you will not achieve accuracy potential.
with bullets seated in the case, they bump up to case diameter and shape.
if this is consistent from case to case it is better.
another way to overcome this is to breach seat the bullet into the rifling (freebore) as scheutzen guys do, or come close by seating a bore diameter (pp) bullet only 1/8" in the case, leaving the bullet with no runout in relation to the axis of the bore.
by neckturning you are creating a brass freebore in exact alignment with the chamber, which we hope is in alignment with the bore where chamber and bore join, but might not be.
keep safe,
bruce.