Hi,
The Act-Labs guns do support off screen reload. They map the second "thumb button" to be the off screen reload buttons for most games. Just remap the thumb button to be reload, calibrate the gun properly and then shoot off screen and it will work.
The only disadvantage is that you now have no third button for grenades and other stuff you might want. For this - I've found a foot pedal switch works best of all.
Cheers!
Doc-