I'd actually been mulling the two piece barrel too NL, mediocre minds think alike and all that. Getting a seal wouldn't be hard using stainless, anyone who's used swageloc knows the drill. Considered either rifling indexed to match (would be easiest with an octagon barrel, mate the flats, and machine so the rifling is seamless), or the reamed to groove diameter second half, unrifled, which would be very easy and still net velocity gains. For a true "pocket fisherman" rifle meant to be packed more than shot, could be something to it.