I am very satisfied with my Puma 92, .454 Casull, with 16" bbl. It groups 1.9" @ 100 yds even though I haven't worked up a best load yet.
It works and shoots great with .454 Casull. It doesn't feed .45LC very well unless the load has a long OAL. That's OK since I don't and won't fire .45LC from mine anymore
The 16 inch barrel adds about 200 fps to velocity compared to a 7.5 inch barrel.
For example, average velocity on a fair, 80 degree day:
Hornady 240 gr XTP-MAG 2233 fps
Larry