1. You do not use an expander mandrel after the neck collet die. The expander is better suited for use with other dies that size the case by sizing the exterior of the neck. The expander mandrel insures that you are controlling the neck interior dimension. The collet does the same thing.
2. There is no such thing as a collet die that sizes the body. What you should consider is a Redding body die. This sizes the body of the case and is used to push the shoulders back. It does not touch the neck. That work is done by the neck collet die. This is an excellent (and inexpensive) approach to controlling the two critical things.
3. There is always someone that will say this step can be forgone, nnd that is true. However there will absolutely be negative affects on brass life, and some reduction is consistency of the final sizing of brass due to spring back. Brass gets work hardened with use. If you don't anneal, the work hardening will have adverse affects. How often you anneal (every firing versus every 2 or 3) is debatable, but annealing or not annealing really isn't if you care about brass life a d consistency.
4. I think there is some confusion about how to measure finished ammo, and seating depth. Let me clarify. CBTO (cartridge base to ogive) is pretty self-explanatory. You need to put your 30 cal bushing in your comparator, and then using you calipers, measure from the base of the case (not the belt) to the ogive of the bullet. This final dimension is specific to your rifle and should be determined by one of two things. 1. What distance you want the bullet from the point of engagement into the lands. .020" is a generally accepted starting point when doing load development. 2. Your magazine length. If you try to put your bullet close to.the lands of the rifle, it is possible that the resulting cartridge length will not properly fit in your magazine (too long).
Understamd that every time you fire a case, the pressure from the ignition (50-65k psi) swells the case and forms it to your specific chamber. The sizing process reshapes the case to near factory specs so that it fits back in the chamber, with proper clearances. Here are the actions that are performed when resizing
**. If using a full length sizing die, the die pushes the exterior of the case body back into spec after being swelled from firing. It pushes the shoulders back from the case expansion that happens when firing (the case grows). It also pushes the exterior of the neck back to a point that is smaller than final dimension, amd then when you pull the case back through the expander button, if final sizes the interior of the neck.
**if using a neck.collet die and a body die, the same functions happen with two different dies. The neck collet die does a better job of sizing the brass without worki.g the brass too much, in my opinion..
PM with any further questions..