No my barrels have fixed chokes.
These are full length rifled inserts. They are threaded at the muzzle end, and have a plastic ejector on them. You insert them from the breech, twist them till the plastic ejector lines up over your metal ejector. Then at the muzzle end, you have an bore sized, um, plug, with a hole offset bored in it the size of the barrel tube. By turning this eccentric around, you can move the muzzle end of the tube inside the barrel. Them you screw on a special nut over the threads to lock the whole thing down. They stick out about .75" past the muzzle.
It comes with 2 different size eccentrics, and the previous owner of this setup had his gunsmith make 1 other pair.
It doesn't work that great, but it does work.
The one they are supposed to come out with uses a jackscrew for regulation. Sight in one barrel, twist jack screw to move other barrel close enough.
The next cheapest alternative is the Kodiak Mk whatever .45-70 rifle, which is about $1400 I think. These can be rechambered to .450 Nitro Express No 2 I think, or maybe it was .450 Nitro Express 3 1/4" or something. I can check and make sure but anway they can be rechambered. Also .450 RCBS which is a wildcat (not like you'd be able to find .450 NE #2 at Walmart anyway).
Next up is a Chapuis at about 4500-5500, although these are overunders and top out at 9.3x74R I think, which is legal for cape buffalo in only one country (Botswana I think, all others require .375 min caliber).