If you’ve not spent much time behind 10.5-14.5” ARs running various suppressors, this entire thread might ‘seem’ like it makes sense. However, you’re just dickering with various degrees of ‘loud’. There’s no way I know of to get a 5.56 in a short barrel to anywhere near as quiet as most anything else in the same length barrel, suppressed. Sure, if you want to run 12” of AB, with 6” recessed, have 6” of rifling and 10” of baffles, or something, you might. Good gravy, talk about dirty as heck! You might get to hearing safe in a 10.5” with some setups, but not all. Point is: I’d probably never waste the time, effort, and $ on an integral 223, just to dodge a tax stamp. Two stamps is cheaper and easier. So is just having a pistol with a brace. That’s just my opinion from running more than a few SBR setups. I hate shooting short 5.56s, even though I have some. Give me a short blackout, 7.62x39, 6.8, ….whatever. The blast pressure on a short 223/5.56 is wicked at the muzzle.