TC Encore .410 barrels come marked .45/410.  Would 410 shells function in a .454 barrel?  I think a .454 barrel would be more useful than a .45.  Any body try it?

Yes the 410 guage shotshell will work on a .454 chambered thompsan barrel. The .45 colt should also work in this barrel as my Ruger super redhwak in .454 will shoot .45 colts also. The one thing that you will want to do though is make sure you clean the chamber really well when you switch from .45 Colt to .454. The .45 colt being shorter will leave built up residue and "Pinch" the case of the .454 round. Hope this helps. Take care.

You made my day!  

The .454 is a streched out .45LC with a case made to take higher pressures.  So any .454 will shoot a .45LC like a .44 mag will shoot .44SPL.