I have used these sets before and will buy more in the future. I teach an armorers course and had a few clear acrylic receivers made. I use these internal parts to show how the military version works compared to the average AR15. they make awesome informational training aids.
M-16 Auto Sear Assembly
This is the same Sear as any Military Auto weapon. However. you will also need the 1/8 inch "Sear Pin" (same length as hammer or trigger pin.)