So far i have only reloaded for my AR-15 where I full length size everything. Recently i just bought a new 22-250 in bolt action and some Hornady custon grade new demension dies for it. I was wondering how to just do the neck sizeing or if i can even do it with these dies? thanks

Blacken the case neck and adjust the die down in 1/2 turn increments until it starts to get close to the depth desired. The black on the case neck will clearly show how far down it's sizing. I go about an 1/8th turn past the last adjustment at the bottom of the neck. That may not be neccesary. I have some Redding neck sizing dies that I now use in two different rifles and they each have a bushing taylored for the rifle. I think this method is better, but I still do use the FL dies for a few others. Nate

Whats a good way to blacken the case neck? and if the die isnt screwed in all the way will it still punch out the old primer?

A majic marker should do the trick. You will have to lower or adjust the depriming rod in the center of the die downward a little. On the hornady dies there is a little nut that you have to loosen to adjust the rod then retighten the nut. If it isn't tight the rod will just move up and down.
You can also buy a Lee collet neck sizing die and be done with it forever. They cost less than $20 and are well worth it.

my 2 cents
Larry

A candle works really well, just smoke the neck a little. Don't get it hot, just smoke it.