308G,
Can you post a good photo where it attaches to the upper? As dang472 stated, there is most likely a jam nut that needs to be backed off first. There is spanner designed for this, or use a cold chisel (after grinding a square shoulder) and tap it with a hammer. Also stated ^ ^ ^, a good strap wrench may work. Again, if it has the jam nut, it has to be broken loose first.
Your profile says "texas" - where? Someone might lend some assistance.