Re: looking for good 308 dies
Lorena, there are a few levels of precision here. You need to decide how deep in you want to go.
1. If all you want to do is squeeze your brass in and set your bullets to SAAMI spec of ~ 2.8", a standard set of Hornady, RCBS, or Redding A series dies will suit you just fine. I recommend using the same brand shell holder as the die set you purchase (the tolerances do vary between brands).
2. If you are using a bolt gun, there is no need to crimp your rounds or purchase any crimping dies.
3. If your rifle was chambered with a "match reamer", you may want a small base sizing die. You may also want a small base die if you are using a gas gun or a lever action rifle. If you have a factory rifle, you won't need a small base sizing die.
4. If you want to have a nice die set, and precisely seat your bullets with a micrometer to a specified depth off your lands, I recommend 1) the Forster Ultra die set or 2) the RCBS Competition die set. You will need a Hornady OAL gauge (or equivalent) with a comparator set for your caliber to measure the distance to your rifle's lands. Use the micrometer to set your bullet back a specified depth; 0.010"-0.020" from the lands is pretty standard.
5. If you want to reduce wear on your brass, you can purchase a neck sizing die. This will only change the size of your necks; it will not bump the shoulder or squeeze the case. Although it is less stress on your brass and makes the brass fit more true in the chamber, there can be issues in getting neck sized brass to chamber properly (especially when dirt or water are present).
6. If you want to size the neck a certain amount to set a certain neck tension value, Redding sells type "S" full length or neck sizer dies. Forster has something equivalent. You will need to buy a neck bushing for the neck tension you want. The full length S die will bump the shoulder and size the case neck in the same operation. The neck sizer S die just sets the neck tension and leaves the shoulder of the case alone. You need to experiment with what neck tension suits your load best. I have two rifles that work best with 0.003" neck tension, but yours might work best with 0.001" or 0.002". Best to buy a set or borrow from a friend to see which works best for you.
7. You may want to control the amount of shoulder bump and the amount of neck tension. To do this you'll want a decapping die, a headspace gauge, a Redding body die, and a Redding type S neck sizing die with the correct bushing. Use the decapping die pop out the primer (so it won't interfere with the headspace measurement). Use a headspace insert with a Hornady OAL gauge (or equivalent) and measure the headspace of a fired case (datum line of shoulder to base of case); you may want to do this for 3-5 cases and take the average. Then, use the Redding body die and bump the shoulder back 0.001"-0.002". This will minimize how much your brass is worked, will ensure it is true in the chamber, and it will be bumped back enough to ensure it chambers every time. Use your Redding type S neck sizer die to set the neck tension. Finally, use a micrometer seating die (Forster, Redding, RCBS, etc) to seat the bullet's depth the specified distance from the lands (wherever your bullet likes to be, say 0.020" from the lands).
Hope this helps you make a decision.