A family member has a Colt 9mm AR with 7" barrel. This was originally purchased in 90's and it had a DIAS with it. He wants to keep the DIAS but sell the Colt bc its old and was also restamped SMG. I said I would ask the experts here. I was thinking, maybe take off the stock and install a Sig pistol brace??? Or maybe the only way is to split the upper from lower and sell individually? Thoughts?