Hello all. This is my first post. I'm thinking I need an AR308 of undetermined brand in 338 Whisper. I have built several AR15s, but this will be my first big gun. I'm in need of a few specifications I have not been able to locate. 1. Gas port size and location for a 338 Whisper (338/7mmBR). This will be a likely subsonic shooter only, although I'm open to flexibility in my build. 2. If purchasing a barrel blank, I use a 1" for the AR15 and turn to the profile I desire. Is that sufficient in a 308AR, or do I need something larger? I greatly appreciate any input.