AirBoss series are basically all the same, difference between models is mainly their looks (the stock).
I have a C5 (black mamba) .22cal.
On the plus side:
The interior mecanism is very simple and easy to understand. Disassembly and reassembly is easy.
You don't realy need to buy stuff to power mod (or detune) since the adjustment screw on the hammer spring is doing the job just fine (actually they just turn that screw to make ''detuned for canada'' models...)
it is unregulated but there are regulators available for a reasonable price.
The magasines are deep enough to accomodate many pellets, even the H&N Hornets fits just fine in there.
With the right pellets and a good scope you should be able to do 50 yard bullseyes no problem.
On the bad side:
It is very loud, even with a silencer on you will ear the hammer bagning hard on the valve with a ''piiiiinnnnnnngggggg'' sound following the shot.
Mine has come with a bent barell you should examine that...
With the regulator installed the aesthetetics sucks a lot and the stock will not hold the bottle anymore.
You need to remove the stock each time you want to turn the adjustment screw, If you want to mod that out you will have to pierce the stock.