Looks like a pellet gun......so is it a pneumatic shotgun?

eldeguello... it's a pneumatic rifle. The machinest rifles his own barrels and incorporates a twist rate acceptable to fire slugs that you might use to reload the .45-70 cartridge. The rifle will fire 510 grain slugs at about 700 fps or you can step down to roundball that will travel more than 1000 fps. I have started casting my own slugs from a Lyman 330 gr. hollowpoint mold.

Python, have you cast projectiles from 'lighter' materials yet.

We used to cast from manganese...you get the diameter without the weight.
Manganese is hard to cast, gives you fits sometimes...

I saw the charge valve on the front and right away knew what it was. What kind of pressure does it operate at?

The heavier the better. More energy. At the ranges you'd be using such a weapon there really isn't a need for anything lighter. It is possible to use helium as propellant rather than compressed air. Helium delivers more energy relative... something like near 50% more actually. They're designed to be charged to 3000 PSI. Some get better strings out of them charing on up to 3400 or 3800 psi. Regular old SCUBA tanks don't hold enough air for one, must have 4500 PSI 88 CF SCBA.

I guess it would be ok for something to tinker with or where you cannot use regular firearms. I'll just stick to reg firearms, bow, blackpowder myself-seems like a lot of trouble to go to just to shoot.

We hear the same thing all the time from dedicated firearms users. I love firearms myself also, but you really learn to appreciate the fun of using something such as air to take game. It has it's advantages as well as disadvantages; just as high powered rifles, muzzleloaders, handguns and bows do. I'd bet that if you were to get some good trigger time in with some high quality, high powered air rifles... you'd want one too (just as many other converts have). It's the love of the sport and the outdoors, it all flows together. There do exist small bore (.177-.25) air rifles and shooters that can and will out-do rimfire benchrest shooters up to 100 meters.

You could consider hunting with big bore air rifles such as this a mixture of bow and rifle hunting. Generally you need to get in close, 50-70 yards. At that distance with a the right slug it'll generally stop just under the skin on the opposite side of a bison. Know your gun and your ammo and it's possible to cleanly take smaller game at 200 yards and beyond. The energy is not lacking. If you should be shooting game at that distance with an air rifle, your skill is not lacking either.

You would have to prove it to me that an air rifle will outshoot a fine target rimfire out to 100 yards. I SERIOUSLY doubt that part.

How do you prove anything on the Internet?

I'm not the person to ask for those groups, I haven't and probably can't shoot anything close. I can tell you that I've seen 1.45" 5 shot groups at 183 yards. I've seen just slightly over 2" from the same man and same gun at 200 yards. It would be a false statement to say that an airgun is not accurate. I'm sure better have been shot that I have not seen, but thats still acceptable in my book.

Added content:

These groups were shot by the same man. He does a lot of testing and his postings on the airgun forums are always very nice to read.

All at 101 yards. Two are under 1/2".

More?

Same guy mentioned above, same gun (BSA Hornet). 5 shots at 55 yards (50 meters). This was shot during a rimfire competition.




Different guy, different gun. 100 yards.