4 rounds in magazine. It is possible to chamber one and "top up" the magazine.
I have two of these. They both do around 2" groups at 100 yds.
I believe the 100 yd effective limit is due to the limitations of the .44 Mag, not the rifle's accuracy.
Because of the tubular magazine feed mechanism, you have to watch case overall length. 1.610" is about it, I think, which may limit you to 240 gr bullets. Loads exist for revolvers with 300 gr bullets, and these probably won't feed properly.
The Ruger has a reliable gas mechanism, but it requires a certain pressure to operate. I use 24 gr of H-110 with Hornady 240 gr XTP's and both rifles work well.
I had trouble with scope mounts. You should use steel mounts and blue loctite. The 44 Mag generates quite a bit of recoil.
If you're looking for one of these, the early ones didn't have a magazine unloading button near the loading ramp. The later ones did. This makes it possible to unload the tubular magazine without cycling the rounds through the action.