here are my thoughts on redding in line dies.... please don't take them the wrong way if you use dies of other makers and are happy with your results!
with the exception of custom dies for use with arbour presses by wilson or similar, i would definitely opt for redding dies or converted forsters.
they are the only dies that will neck size uniformly and concentricly and the are the only dies that will seat the bullet concentricly, because the case is held in a chamber that then slides up into the die.
when using the dies this is what i do:
1. neck turn my cases to a uniform thickness, trying to remove the least amount of brass as possible. you need to have uniform neck wall thickness to ensure that you have consistent neck tension when using bushing dies. people that tell you don't need to neck turn lapua brass (for example)are talking rubbish, all brass has variation and this needs to be uniformed by neck turning.
2. prepare a loaded round to your desired o.a.l and measure the outside neck diameter using a micrometer capable of reading to a tenth of a thou.
3. you need a bushing slighlty smaller than this, how much smaller depends on many things from the size of the calibre, the amount of tension you want, the hardness of the brass...
4. in terms of accuracy, you want as little tension as possible to ensure that the bullet is not going to move or be affected by recoil. i go for 1 - 2 thou tension for hunting ammo, but i don't use any seriously kicky calibres...
if a loaded round measure .263 for example, i'd buy a .261 bushing and try it first. in theory, this should size to .261 and allow a little spring-back of the brass to around .262 giving a thou or so of grip.... in theory.
a couple of things to consider are that freshly turned brass will thin out after a few firings so neck size to about 1/3 of a thou over the final size you desire
if using the redding comp dies, you only need to neck size down 2/3 of the length of the neck. this will mean that the remainder of your fire-formed neck will be tight in your chamber and offers you some of the centralising benefits of using a tight neck chamber using a saami chamber.
if you use the body sizing dies to bump your shoulder to allow for easier chamber, do it after you have neck sized to ensure concentricity.
hope this is off some use....
i only use redding comp dies so maybe i am biased in my opinions. i wouldn't use anything else and they allow you to work to tight neck levels of accuracy using standard factory chambers....
any questions then please feel free to ask and i will try to help if i can
kind regards
derek