Well I finally got off my lazy old duff and did a little homework....and I'll have to correct my prior post. My barrel marked ".45Colt" is NOT chambered for .410 ga. shotshells. rwsem, you are exactly correct sir, they are chambered for .45Colt to be used with shot capsules loaded in .45Colt brass. A 3" .410 shell will not go in my barrel...a 2.5" will. However...I found a fired 2.5" shell case and tried it...NO GO! So I got out my old catalogs and also a recent article in "One Good Shot" and found the following: TC originally offered the .45Colt/.410 chambered barrel in about the second year of Contender existence and then very quickly dropped it voluntarily from the line-up after disscusions with the BATF. The company then offered the .44mag Hot Shot barrel, Hot Shot capsules, and ammo. The .357 Hot Shot soon followed and along with it the .45Colt barrel w/ choke for those who wanted to load their own .45 shot capsules. .45Colt Hot Shot capsules or ammo were never offered. Catalogs #1(1974) through catalog #12(1985) show these ".45Colt w/ choke" barrels available. Catalog #13 re-introduces the .45Colt/.410 barrel. About halfway or a little more through this period these barrels were all octagon 10" (including the external choke), and then the bull barrels became available.
I don't know nor have I ever heard that it was unsafe to fire a 2.5" .410 shell in one of these barrels, but I would have to think that extraction would be a little difficult. I would think that if it was a big deal TC would have put some notice in their catalogs which I do not see.
GOOD SHOOTIN', Walt