Stan, not a jug choke really but the inverse would be a Beretta 390 Super Skeet barrel. Choke is 6-8 inches down in the barrel with about 3 inches of tapered expansion chamber in front of the choke to the muzzle. Like a Tula choke.

I've had some discussion with the guys at Charlie's shop. The think they can replicate it with a Comp N Choke tube.