[Uncle Alvah]

What is the difference between a dedicated neck sizing die, and using a full length die adjusted so as to simply resize the beginning of the neck?

[Steve C]

Having to mess with the adjustment.

[ranger335v]

A neck die won't touch the case body while a partially FL sized case will almost always have some amount of case body contact. That contact pushes the shoulder forward a bit and makes for hard chambering.

In other words, there is a valid reason neck sizers are sold.

[kelbro]

I prefer a collet die/body die set up to move the shoulder back ~.001" combination myself.

[ClarkEMyers]

A dedicated neck sizing die can be used to make contact with the shell holder and so sometimes align more precisely. Most die and press combinations have a fair amount of slop in the threads and some people like to touch the shell holder to square up the die - see e.g. the Redding shell holders in assorted heights to allow both length adjustments and contact. Partial resizing changes the case and touching just the end of the neck may bend the neck just a little.

Of course with care there are lots of variations that can be worked to produce good results with a particular set of components reloading gear and firearm.

[Stinger]

I like neck sizing. I've done it with all three methods: full-length (adjusted to neck size), dedicated neck sizing dies, and collet dies. They all make good ammo that shoots better than I do. It sure is nice not having to lube with the collet dies, though.