What type of co2 air rifle has long firing range?

The C02 air rifle that has the longest firing range is the PCP (PerCharged Pneumatic) class of air rifles.

These include rifles like the AirForce Condor, Benjamin Marauder and the Benjamin Discovery. But these are expensive air/C02 rifles. They DO NOT use the 12 gram powerletts but require an expensive support system. The next strongest class of air rifles are the Under lever, Break barrel or spring/Nitro air rifles.

If you want to understand more about air gun systems then read the link below (It's part of my profile) read the section on "Air Gunning"