.223 reloading questions

[toxic]

I've been reloading .40 SW for abour a year. Now I'm getting into reloading .223 for my AR and I have a couple of questions before I actually start. I'm using a Dillon 550B with RCBS small base dies (2 die set) and I bought a basic lee case trimmer dealy that you spin by hand.

When I adjust my resizing dies is there a way to know if it's adjusted right without a case guage (I don't currently have one). I have a dial caliper but I'm not sure what I'm looking for. Am I concerned about length of the neck or diameter? I think I'm looking for "headspace" but I'm not sure what that means exactly...

 

[proonur]

The way I do it is that I put in the die and run the press up until it just touches the sizing die base when fully extended. Then I back off the press and turn in the die another half turn, and I'm good to go. Have had no trouble resizing brass this way thus far.
As far as the case dimensions go, your reloading book should give you exact sizes for each section of the brass, but in all honesty your AR will be pretty tough on the brass anyway and I'm sure you won't have to worry about running out of neck length cuz you'll only get maybe 5 reloads out of a semi auto from what I've seen... maybe fewer. If you don't have a book with the dimensions just tell me what bullet you're loading and I can give you the info out of the books I have here.
Headspace can't be measured without a proper gauge, so don't worry about it.