That is a PCP or pre charged pneumatic. You can get them in any caliber you wish. Quackenbush  makes an incredible .50 cal.

 There are a few revolving carbines available in up to 9mm that are mass produced in Korea and are told to be quite well made for the money.

 You can fill them from a scuba tank, or you can buy the larger tank like your oxygen for a torch. Or,....you can buy a compressor. But most people go to a paintball sales to have them refilled. You only get about 6 shots at near full power. After that, the power drops off pretty fast.