my local gunshop has an AWESOME suppressed rifle on the shelf. chambered in 44magnum handgun round. barrel and suppressor are one piece and much wider than most suppressors. perhaps 3". i haven't shot it, but i'll bet it's pretty quiet. it's not that expensive either, but I pared my collection down to just a couple calibers and 44mag isn't one of them, so i passed on it.
i have been considering getting a suppressed rifle chambered in .480 ruger. i already have a taurus raging bull and rossi '92 lever gun in that caliber. it's a cool caliber because it shoots a massive bullet at relatively slow velocities. that seems more appropriate than the current crop of hand cannons (500sw, 460sw, 454c, etc) i load mostly 400g gold dots.
now, the trick would be finding a magazine-fed bolt action that would feed it.