Going back to the original question:
Quote Originally Posted by Texas Solo View Post
I have 1000 rounds of once fired Winchester 5.56 brass. I know the difference between 5.56 and .223 loaded ammo, but I'm unaware of any difference in the raw brass. I do know that military (LC) brass is thicker and can increase pressure, but I'm talking about Winchester brass.

Is there any reason why I can't load the 5.56 brass to .223 specs and use it in my #10PH with it's .223 chamber??

I plan on using SB (small base) die for the first loading, then fire form and neck size after that.
The short answer to your post (You've already read the long, long answer) is that yes you can.

Just as you should any time you change components, you should work up from a minimum published load to something that works safely in your rifle instead of simply starting out with a hot load that worked well with a different (insert your choice: bullet, primer, powder, brand of brass, rifle, wife, etc...)

As others have mentioned, you will need to make sure the primer crimp (if there is one) has been removed one way or another, and small base dies are probably not a necessity. I've taken military brass, cleaned, prepped, swaged the primer pocket, full length resized, and it works like a champ.

As with any reloading effort, all standard safety rules and warnings all apply.

Bottom line: It's just not that complicated.