I was having catch issues with my Indra when using any spring stronger than a k31, and I have heard many others are as well. This plunger fixed my issues. I highly recommend using an extended spring guide along with this part.
This plunger requires about 6.5 inches of standard Caliburn threaded rod, and two nuts. The stem is designed to be tight on the rod, and you should have to almost thread the rod into the print. It should stick out about half an inch from the front of the plunger head, used for grabbing on to and twisting with pliers, and not stick out from the back. I recommend using threadlocker on the nuts.
The author remixed this model.
Significant changes and tolerance adjustments to plunger rod and head.