Okay, I've got a HiVel .410 adaptor, and a Dina .38 Spl adaptor. Both cycle just fine through M1100's and 870s (manually). I've shot the Hi Vel, and it shot okay, I guess, but the puny 90g .410 slugs didn't even dent the mailbox I shot with them. Not real impressive. I'll probably just keep that one loaded with heavy birdshot.
The .38 shell is actually rifled, but it's an AL barrel, so I don't think that I'll be using any jacketed in it. I've got some full wadcutters loaded that I'll try in it, for fun. Haven't had the chance yet.