[mcguyver]

Some guns have been known to have issues with wiring position in the grip. I have had this issue with G&P guns in the past. If the wiring is not routed precisely, with bends in the correct places and connection done in a certain order, the motor does not sit properly aligned in the grip (and the pinion gear aligned with the bevel gear) and those guns would simply not fire.

Now, having never worked on a 416 and not likely ever to, I'm only speculating here. If the gun is stock, and all you are doing is changing the motor, then your issues are likely to be there. Ensure your motor height and position are correct. I find it unlikely that a CA motor will work just fine where a Marui and Systema give you problems. The key must be in the installation.