DPris said, in reference to oneof my remarks,
Rifling gives the shot column a spin, and centrifugal force opens up the column. Saying "it doesn't upset the shot pattern too badly" could not be more wrong, at least in the one I tested.
I did not mean to imply that
I thought "the shallow rifling would not upset the shot pattern too badly," but rather that that was apparently the philosphy of Taurus.
Anytime you spin that shot charge, you are going to get extra dispersal on exit from the barrel, usually in a doughnut pattern. As I see it, there's no way around that, and one simply has to recognize that shot shells of any kind out of a rifled barrel are strictly very short range propositions. Like maybe three or four feet, and that's that. As I said, you have to recognize the limitations.
Thompson-Center, I believe, provided a barrel for both .410 and .45 Colt for their interchangeable-barrel pistols with a screw-on adaptor for the shot shells which had straight rifling. This was in an attempt to stop the shot charge from spinning after going through the regular rifled portion of the barrel. The straight "rifling" supposedly stopped the spin of the shot charge to allow tighter patterns.
I think they also had a mild choke on the adaptor... with the lands cutting deeper toward the muzzle end of the adaptor.
This was in yet another attempt to get around the smoothbore-pistol legal problem.
I don't know offhand if they still market that variation on the theme.
There are times when I think it's unfortunate that .410s and .45 Colts have about the same dimensions on their rear ends so people wouldn't have to keep trying to make the concept of .410s in .45 Colt chambers work... somehow.
The real solution is to change that portion of the NFA which proscribes shotgun barrels of less than 18". And it would be for the children... protection against snakes while walking around the boonies with a couple of kids, doncha know.