C3k I expect you will be in for disappointment if you want a replacement with the exact same spec's as they haven't offered that particular barrel for a while now, hope you get lucky and they can find one stuffed in a back corner of their parts room if they can't spin a new extension on the current barrel.
Eta: my bad still have the fluted 18, I mixed it up with their newer 16.
Eta: my bad still have the fluted 18, I mixed it up with their newer 16.