Big bore airguns are very, very loud. I have a Benjamin Bulldog, which is considered kinda at the low end power wise of big bores, and I need hearing protection to shoot it. I run a DonnyFL Emperor, which quiets the gun down significantly! But on the mega powerful big bores, I don't know how much that will help.
I use a 45 min Carbon Fiber SCBA tank filled to 4500psi and that gives me around 200 shots in the sweet spot of having consistent velocities. I have two tanks, and they are fairly light weight, but I'm not so sure I'd strap one of these on my back and hike out into the backwoods.
As far as range for game goes, well, it depends. We don't have legal deer hunting in Ohio with airguns yet, so I can't personally comment, and I went out a few times for hog, but those SOBs are hard to come buy in my area. With that said, I've taken racoons at 120-130 yards with body shots easily. I figure in all practicality, this is a 50-75 yard deer/hog gun stock.
The thing to remember with these guns, is they get their fpe from shooting heavy ammo relatively slow. So longer shots have one heck of an arc, which means ranging your target and knowing where you need to target for holdover/under means everything. I use an ATN X-Sight 4K Pro scope, which has the built-in Ballistics Calculator, so I don't have to fiddle with all that.
I know the Hammer seems attractive, but I wouldn't purchase one myself, as they had way too many production problems, and who knows what is lurking that has yet to be discovered. For the super big bores, go Air Force Texan CF in .457. They have been doing this longer than anyone, and the only downside is they don't have a magazine for quick follow up shots. Hatsan also has come out with their PileDriver guns in .457 and .50 cal. I like Hatsan guns, for decent performance without destroying your wallet, but the Piledriver is relatively new, so the jury is still out on reliability.