So I just won an Aero Precision AR chambered in 224 Valkyrie....I'm not very familiar with this caliber....i do know that I cannot shoot 223/5.56 out of it, but my question is, can i just swap barrels and BCG and keep the existing upper? Or would I have to swap uppers as well? The gun was built by a coworker and it was donated for he raffle at our company christmas party. It is brand new, never fired. It was cerakoated with a subdued stars & stripes, so I'd like to keep the upper and lower. The barrel is a Seekins Precision, pretty sure it's an 18" barrel and the BCG is Aero Precision.