I'm on my sixth .30-30, I've owned two Marlins, three Model 94 Winchesters and a Savage 340 Bolt. All were accurate and fun to shoot, but I only took game with one of them; a post-64 Model 94. It killed one whitetail and a couple of bears quite handily. For virtually all practical deer hunting, they are really only limited by their sighting equipment, when one considers that about 95% of whitetails are shot within the .30-30's range of about 200 yards. If you have a decently accurate Mossberg, Marlin or Winchester lever, scoped, you have a fine deer rifle out to 175 or 200 yards. With the as-issued open sights, I'd say one can shoot deer-accurate to about 125 or 150 yards, and a bit more, maybe to 200 yards with a receiver sight and some practice.
The longest shot on deer that I can personally vouch for with a .30-30 was made by a friend of mine in Alberta several years back. One-shot kill on a decent 10-pointer using a Model 94 Carbine with a Williams receiver sight and small front bead, factory Remington 170-grain Core-lokt ammo. My friend used a boulder for a rest and had lots of time to shoot a broadside, grazing deer. We paced off the distance at about 250 paces, and figure the shot was an honest 200 to 210 yards.
The very few reviews I've read on the Mossberg indicate a rifle that should be on par with the Winchester and Marlin rifles.