Well I am not sure about AK's, but if you want to do a little reading to educate yourself a little more, just google 80% AR lower. From what I have read, it is completely legal to build yourself a gun out of parts and an unfinished receiver so long as the following conditions are met:
1) You do all the work yourself. You can not outsource the job to any machine shop or even a friend.
2) You do not sell, transfer, gift, or in anyway get rid of the firearm to someone else.
As far as the local LEO, many police don't know all the laws. There is so many I don't know how they ever would. So some more googling might produce the letter from the ATF or some other law that could be printed off and shown to anybody that happens to question your fine workmanship.
1) You do all the work yourself. You can not outsource the job to any machine shop or even a friend.
2) You do not sell, transfer, gift, or in anyway get rid of the firearm to someone else.
As far as the local LEO, many police don't know all the laws. There is so many I don't know how they ever would. So some more googling might produce the letter from the ATF or some other law that could be printed off and shown to anybody that happens to question your fine workmanship.