I have purchased a 7.5" 300BLK barrel. I was planning on swapping parts out. I have zero plans (because I value my life and safety) to fire .308 ammo in a .223 barrel. After consideration, I'll get a separate adjustable gas block and tube. When I said I wanted to use it for both, while I want the option to be able to fire 5.56, this is primarily for home defense where the 300blk is a much better option for me (less flash, noise, potentially attach a suppressor). So almost all of the time it will be set up that way, and only if I sell it or decide I want to change, would I swap the barrels back. I would have purchased it in a 300BLK from the get go, but with inventories and availability I could only find it in stock in a 5.56. While it may be a tempest in a teapot, I'm concerned about the potential for executive orders making it difficult or impossible to purchase AR pistols in the future which is why I did not wait to get exactly what I wanted rather than compromising.