I have a Hills and drypac which I bought s/h off here. So far it is excellent and for my use (pumping an HW100 to 200 bar) for hunting where I generally fire off perhaps one or two mags in an evening it is ideal. Roughly one shot equals one stroke of the pump equals one bar.

As for reports of it being hard work, well I think this is piffle and I am no superhero. As said in previous posts just use straight arms and your body weight and get on with it. No wonder the nation is so obese !

If you were blatting away hundreds of pellets at a time on a range then you would find cylinder useful.