Re: 223 COAL....
You will generally find the recommended COALs in the loading manuals, associated w/ each bullet type/shape. (See here):
Those measures are usually derived from a combination of a needed shank depth in the case neck, and the bullet nose curvature. Do not
expect the distance-to-rifling to be the same for different bullets even though the COAL might be the same. Case in point w/ my Krieger-barrel AR: The 77gr SMK seated to 2.26" will be 10 thousandths off
the rifling. The 52gr SMK seated to that same 2.26" will be 15 thousandths into
Cannelures (if on the bullet) are generally placed to accomodate recommended OAL for that bullet w/ nominally trimmed cases. Seat to mid cannelure to start. Adjust from there. (FWIW: I and many others do not crimp as a rule. Neck tension more than suffices for consistent ignition and cartridge handling)
(Note: Precisely determining optimal bullet stand-off from the rifling is another kettle of fish altogther. Best start w/ reliable functioning as a design basline)