Helium vrs. HPA any power difference?

If you want to get a good idea of the power potential of helium vs hpa, check out the Extreme Big Bores website. For some of their guns they show a table with the energy for both air and helium. The increase with helium is considerable. They are getting 1400fpe on Helium with some of their air rifles. Those same rifles were getting 450-750 fpe with air. 

You can use helium in any PCP gun and it will increase the power. The only mod needed is a lighter hammer spring tension or some guns will empty the entire tank with one shot.