Though the Airsporter MK4 onwards and Mercury pistons are interchangeable, the Hawk2/3 Pistons and Osprey Pistons aren't, Guy.
The Hawk has a cocking lever slot in line with the piston sear cutout, the Osprey has the cocking lever slot at 90 degrees to the piston sear to accommodate the sidelever layout.
Yes, it's been said that Webley drilled a void into the front of the Osprey and Hawk Pistons to lower their power for the German market.Originally Posted by ggggr
All the best Mick