Alan -- Very interesting to hear that a .454 Casull cartridge will chamber in your .45 LC rifle. Does your .454 reamer go all the way in to the chamber?
Sounds like the situation with so many .357 Mag Handis, including mine: .360 Dan Wesson chambers just fine. When I got some .357 Maximum brass to work with, I trimmed ten pieces until they fit the factory chamber, and they measured longer than .360 DW factory brass. That's when I decided to go ahead and lengthen the chamber to .357 Max.
I used a hand tap wrench and generous amounts of cutting oil, just the Oatey oil used for thread cutting. First I compared a trimmed Max case that fit the factory chamber to a full-length Max case, and proceeded to cut very slowly and with little pressure. As the rim of the reamer reached the barrel's existing rim, I slowed down even more, and just "feathered" it home, to avoid cutting the rim too deep. The leade of the rifling is so far out in the .357 factory chamber that the Max reamer only removed metal from the case mouth area, and none at all from the origin of the rifling.
You may not have to do any cutting at all. Let us know how deeply you have to seat bullets to chamber your loads. I am not able to seat any .35 caliber bullet far out enough to touch the rifling in my Max barrel, and have finally settled on seating at a crimp groove for the sake of durability in the field. When you're done, you should have a terrific little woods rifle for whitetails.
