I saw a hunt where Tom Kelly from S&W dropped a Grizzly or Brown (not sure which) from about 75 yards with a 6" PC 500. Given the barrel length, and knowing what mine throws for unburnt powder I would think your Puma could out preform.
Beg, borrow or steal a crony, and do some math. Not to discount Pathfinder's success with a 30-30, but when caliber shopping there is always someone telling you that a certain animal is an easy kill. I remember shopping for a big game gun and using a list of deer, to elk and moose, to Grizzly. Everyone said not to worry about a moose, because they are an easy kill. I trusted this until I talked to a couple friends that were on a moose hunt while I was shopping. They put three 270's in a moose before the other's 30-06 took it down the next day. Shot placement and energy are both needed.
One advantage I think the .454 will have over my .500 is bullet shape. The .500 has a lot of power and a lot of mass, but it is not very aero dynamic. It reminds me more of a shotgun slug than a bullet like the .454 has. That said, I am hitting a 20lb lp tank at 100 yards and all the way out to 200 yards off a rest.