My lifter had a bit of an issue that when i racked the pump back too fast that it would fall down too fast and bounce a lot.
the bouncing lifter would then quite often be in the way of the shell that gets released from the tube and result in a jam.
This modification aims to dampen the fall and bounce of the lifter a little to prevent that, i used a 17mm diameter and 3mm thick pad of felt used for door knob stops on walls or on the feet of chairs, you can get them in most hardware stores. You have to cut the pad in two and install it like shown in the picture, and it should end up on just about the right lifter elevation.
The author remixed this model.
This is just the lifter part, with a cutout for the felt pad. Print with the suggested values for the original lifter.