Hello, new guy here with my first post.
Great article and well done.
I did find one thing in the article that was in error however. This.
If you are a handloader, you must also consider that the 5.56x45 mm cartridge case may have a thicker sidewall and a thicker head, which were designed to withstand the stresses generated by the higher chamber pressures. This reduces the powder capacity of the case. If the 5.56x45 mm case is reloaded with powder charges that have proven safe in .223 Rem. cases, this reduced internal capacity can result in much higher chamber pressures.
Sierra and many others have shown that this is indeed incorrect. In fact not only does 5.56 brass NOT have less case capacity then the 223 often times it has more case capacity than 223 brass.
Here is a little from Sierra on the subject.
The conventional wisdom to reduce loads with military brass is familiar to most reloaders and is generally good advice. The rationale here is that the military cases tend to be somewhat thicker and heavier than their civilian counterparts, which in turn reduces capacity and raises pressures. This additional pressure normally requires a one or two grain reduction from the loads shown in most manuals or other data developed with commercial cases. While this is most often the situation with both 308 Winchester and 30-06 cases, it is less true with the 223 brass. We have found that military cases often have significantly more capacity than several brands of commercial brass. Again, take the time to do a side-by-side comparison of the cases you are working with and adjust your load as needed. There may be no need for such a reduction with the 223. Know your components and keep them segregated accordingly.
I found this as well. Scroll down to "223 Case Weight vs Capacity". Note the highest capacity is 5.56 brass.