I didn’t address the issue because there was no issue. If you pick your brass, primer, powder, and bullet, whether you use 5.56 or .223 data, you will end up at the same result when you finish working up your load. That’s why people don’t need to worry about different sets of data.
No, you will not end up with the same results because the standards are different. I mean, a couple pounds is the same as a kilo, right? Sure, unless you have to carry that delta in weight all day long. Apparently you are not educated enough to understand the interaction between a change in chamber dimensions (which we haven't discussed) and what a difference in pressure transducer location, as well as MAP pressure, means for a cartridge. You are a troll who has read a few reloading manuals and think that it makes you an expert, but who am I to disagree? I apologize, let me try again and repost my response.
You are the greatest ever Havok1, all bow before your knowledge! I'll take a cue from you and won't bother to post data or references because you are right! There is no difference between the two and you know more than anyone else! You'll certainly post the data from your pressure barrels to this forum to show that, right? The next post you make will have pressure traces showing that data from your 223 pressure barrel and 556 pressure barrel that are exactly the same when using identical powder, primer, brass, and projectile. Let's see those traces, post them here, please! I am wrong to question you and you next post will admonish me thoroughly with the traces showing how little I know.
Don't forget to post your data from the SAAMI approved proof loads that you used to calibrate your test barrel (which brand is your test barrel, did you get a Wiseman barrel or did you slum it with a European knock off?) so we can verify it against our setups. You'll also include your NATO approved laboratory data for the 556 results (oh, who made your setup and did you get the solenoid operated firing pin option? If so, how did you get rid of the bounce in your transducer signal return and if so, did you choke it front or back, it's killing me), right? Oh wait, let me guess... you couldn't get proof loads from SAAMI (hard without being a member, they are suck hard on that, but you got a box or two somehow and followed the instructions to the letter to calibrate to the industry standard, right?) and you haven't bothered to certify for the NATO spec (you did pay the fees and followed all the protocols to be certified, don't we all?) so instead you have the calibration data from your transducer manufacturer (who made your transducers and you are willing to share their trace letter with us so we can verify them?) to proof your test barrels? Post those data, it's enough for us.
Oh wait, let me guess... you can't but you have an oil calibration setup (baller option big daddy, you have some money to spend and bought it from... wait, whom did you buy your setup from? Did you spring for the automatic electric pump or did you go cheap on the hand option?) for your garage setup and you calibrate your transducers on your own because calibrating a transducer is child's play, and you are an expert on how to do that! Please, post your traces and let us all take a look at them. Oh great one, please, humor us serfs with your greatness! You have those data right? Your next post will include them, yes?
Oh, I'm sorry, I forgot. Silly me. You spent thousands upon thousands of dollars building a ballistic testing laboratory in your garage and aren't willing to post those data here for us to see because it would undermine years of hard work developing those data for your own use. That's how you came to your brilliant conclusion that there is no difference between 223Rem and 5.56 data when properly developed and aren't willing to share with us. I understand, I do! It's hard to be in your situation, it really is. I mean, I am too, imagine that! How to balance sharing your knowledge with us, the commoners. It's tough. The best option is to write silly posts here and feel good about it. Thank you for your great and important contributions to the discussion addressing the OP's question! There is no difference (even though there is) between 5.56 and 223Rem and you won't talk about how or why, we should just trust you because you read a reloading manual once or twice and that makes you a subject matter expert! Gosh, why didn't I think of that?
For the rest of you who care, here it is again. The general rule, from actual pressure data, is as follows for 223 (SAAMI) vs 5.56 (NATO). For the same exact bullet, the 5.56 data will normally show a higher powder charge and velocity due to the different MAP, transducer location, and chamber dimensions for the 5.56 specification. That is contingent upon the data coming from same laboratory and using pressure barrels setup for those two specifications. Unless you have access to THOSE data, which some of us do (imagine that, some of us do!), find the published load that works best for you and your rifle. Understand that there is a difference between 5.56 (NATO) and 223Rem (SAAMI) specifications and while it may not make a difference to your situation, there are differences between the two. Work up carefully, find an accurate load, and be content with it instead of chasing the greener grass from another spec.
Back to the current post and ignoring the OP's question. Have no fear, Havok1 is going to post a bunch of pressure traces from his test barrels to prove me wrong in just a few minutes... Wait for it, it will be worth it. I'm giddy with anticipation to see those traces as I'm sure everyone else is as well.