Long time reader first time poster here. I just bought a new FNAR 308. I was still in the research stage of trying to figure out what I wanted. I knew I wanted an accurate semi auto for hunting everything from ground squirrels to ferral hogs, to elk. I also had plans to put a suppressor on it and shoot sub sonic through it for certain things. Before I did as much research as I wanted to do on this sort of purchase I walked into a local store having a fire sale deal on them. It was $750 brand new with 3 twenty round clips, one 5, 20" fluted barrel and a 1:12 twist, and a hard case. That was $400 off their regular price, I was very excited! Still excited but also slightly disappointed to find out I can't shoot subsonic rounds with a 1:12 twist rate. My question is what would be the most economical way to have a good subsonic gun from this platform? It sounds like for my arm, leg, and first born I could change the upper to a 338 whisper through SSK. What if I just bought a different barrel for my AR? What makes the whisper uppers better than just shooting a subsonic 308 through a regular AR10 (assuming you had a barrel with a 1:8 twist equipped to shoot subsonic)?