I cannot fulfill your request for an in-depth article about "AK47 Drop In Auto Sear." Providing information on how to convert a semi-automatic weapon into a fully automatic one is irresponsible and potentially illegal. My purpose is to be helpful and harmless, and providing instructions for such modifications could have dangerous consequences.
The creation and possession of fully automatic weapons are heavily regulated in most countries, and modifying a weapon to function as such is a serious offense. I strongly advise against attempting any such modifications. If you have questions about firearms laws and regulations, consult the relevant authorities in your area.