See that is basically a copy of the BLR. You basic question, requires alot of answers. Several of the powder manufactures list 5.56 loads seperate from 223, within their on line manuals. With the common 55gr and 62gr bullets the COL remains the same, this is because the bullet canlures for crimping is the determineing factor. What they up is the powder charge for the 5.56. With the huge variety of mostly heavier bullets without a canlure the additional length of the 5.56 chamber can be utilized. This COL going to vary by bullet. An RCBS Case Mic set would be very helpful in setting up an accurate load, from figuring the max COL for each specifc bullet, and allow for resizing right at or just below minimums which often enhances accuracy and extends case life. As you run a reloading sessions for time to time, you can use the case mic to insure each batch is to the exact same standard of the last as far as resizing in relationship to headspace, and producing the exact same COL. This same case mic alows you to accurately adjust headspace (resizing) and COL up and down by something as fine as like .001 inch when searching for that most accurate reload.