Runout comes from more than necks, like body and seating.
I agree that that true FL dies(which are not body-bushing dies) introduce low runout -provided they're fitted to fire formed cases, and minimally size. Otherwise the brass will give you runout while springing back with thickness variance. Doesn't matter how straight a die is here, or about body support, if sizing a lot.
But I would not ever FL size necks. So if I went this route, the FL die would be modified for partial neck sizing(without a bushing).
Then again, I like bushings, and adjusting neck sizing length(tension). I haven't had an issue with runout from them. So I'll stay that route.
I agree that that true FL dies(which are not body-bushing dies) introduce low runout -provided they're fitted to fire formed cases, and minimally size. Otherwise the brass will give you runout while springing back with thickness variance. Doesn't matter how straight a die is here, or about body support, if sizing a lot.
But I would not ever FL size necks. So if I went this route, the FL die would be modified for partial neck sizing(without a bushing).
Then again, I like bushings, and adjusting neck sizing length(tension). I haven't had an issue with runout from them. So I'll stay that route.