After watching the video (several) times, I was able to figure out that this is a very simple lever-locking action, where rubber-band-loaded finger gets in the way of the priming bar, though it was very hard to make out. Have someone film you next time, or rest the camera against something so you can better display the product
Good idea mechanically, but please edit your post to include a few more close-up photos to better convey the action to other users. I also took the liberty of adjusting your formatting. Start a new line after each photograph, it makes reading a lot easier, and just looks a great deal less sloppy.
EDIT: Additionally, try smoothing out your slots, you will get not only a smoother prime but potentially better performance.
Edited by Aeromech, 03 December 2016 - 05:16 PM.