Cut gearbox shell Published December 8, 2014 at 3264 × 2448 in Magpul PTS Masada Wolverine Airsoft SMP Conversion Cut gearbox shell The gearbox shell was cut (only the right side) to allow the SMP to be extracted from the gun without removing the gearbox from the lower receiver. Note there is a slot cut to make room for the bolt cover lock lever.