44 mag out of a rifle is a much more impressive round than out of a handgun. If your rifle will shoot heavier bullets in the 290 to 300gr range this is what I would use. If you reload I would look into either a quality cast bullet or the hornady xtp in 300gr. I believe Sierra also makes a 300gr JSP that would work as well.
If you don't reload then I would look at finding a company that loads a quality heavy bullet. Double Tap loads a 300gr Nosler bullet. If your rifle twist will not stabilize a heavy bullet then I would look at getting a bonded bullet or a mono-metal bullet such as a Barnes that will retain it's weight and penetrate.
You will see as much as 200fps gain from a carbine vs. a 6" handgun. This will produce a little more energy and aid in penetration.
