I have done a couple of pure mech pump bushies though I wasn't pleased with the outcome on the sonic with the electro pump. I made it to allow autotrigger but the recoil on the bolt when not holding the pump handle tended to just make it go full auto. It was just a switch wired in series with the trigger that was engaged when the pump/bolt were forward.
as mentioned I don't have my pword with me to get on ICDO but these are mine.
the BKO has an under cocking kit now but really doesn't chrony over 200. I used it for reball when I lived in Springfield.
if you have the materials and the tools it really isn't a hard conversion, your just turning it back into a sheridan.