A buddy and I are making double slug guns, i.e. taking double barreled shotguns and making a "poor man's double rifle." Colonial chokes say their rifled chokes are so thick (the part that sticks out in from of the muzzle) that two will not work on a side-by-side. Anyone know of rifled chokes that are thinner than the Colonials?

I'd install one and sight it in, then turn the threads off the second and silver solder it in place. Machine or file down the part of each that interferes (so there will be a flat on each)and try to move it around under heat to get the second barrel somewhat regulated.

I don't see how they would be too thick at the muzzle to install. Have you attempted to use any rifled choke tubes in any doubles?
Come to think about it try to find a friend who has a rifled choke tube and ask to borrow it and take the measurements.
If a shotgun's threaded for a choke tube, and it accepts most of the other choke tubes, than most likely it will readily accept most rifled choke tubes.

www.briley.com 800 331 5718 they can make tube for almost any shotgun.

The problem is that, although the threaded part fits fine in the barrel, its the part OUTSIDE the barrel, containing the rifling, that is too thick for two chokes to be installed. Mark, your idea seems to be the best solution, just was hoping I could use both rifled chokes and shot chokes to increase the versatility of the gun. Well, boys and their toys.