It's funny how these larger calibers, 44mag - 500mag behave with different size bullet's. My M-29, 8-3/8" barrel would shoot a fist sized pattern at 50 yards with a 250gr factory round. With a 170gr Federal HP the gun had a VERY sharp kick and my pattern was about 12" at 20 yards!!!
I've found the same is true with my 500! I was given some rounds by my dealer when I bought the gun: 270gr HP Federal Vital Shocks and some Winchester 400 gr HP Platinum Tip's. Also I bought some Winchester 350gr HP Reduced Recoil rounds. In my opinion the 270gr was the worst of the bunch as far as recoil because it kicked like a REALLY hot .357 mag load! Very sharp kick and I don't think it would prove to be a very accurate round for me..
As far as the other 2 rounds, both had a lot smoother recoil with the 400gn naturally having the most recoil but both were entirely controllable and comfortable to shoot!.
I decided to reload and have settled on the 350gr Hornady XTP HP for hunting and the 350gr Berrys coated SN for target practice using Titegroup. I've just got to make it to the range so I can try different charge sizes and find out just what makes this gun Happy!!
Have Fun with yer new toy!!