I believe there is a firm selling 7' or 8' long barrels for domestic shotguns. As I mentioned before, I can't find the link.
Since there is no "device" being used (not even a "choke tube"), these are quite legal (and this is what I thought my link went to )
Since there is no "device" being used (not even a "choke tube"), these are quite legal (and this is what I thought my link went to )