Thanks Mike, sorry for the late response.
Let me know how the new mags work when you get them, that may be the best solution. I've had the cylinder open to inspect the mechanism and can't see an obvious fix, there is a spring in the nozzle system that I may experiment with. The strength of the nozzle spring seems to govern the speed that the nozzle retreats (the sooner it retreats the more time the bb has to load into the hop chamber). The problem though with making the spring weaker is that this same spring is also used to press the nozzle against the bucking creating an air seal.
I think I may start by putting in a braking mosfet to get consistency with the starting position of the sector gear.