I am going to be putting up for sale a bren 805 and a few bcm upper receiver groups. It has been a bit since I sold anything so I wanted to make sure nothing had changed.

If I am selling the rifle in state or out of state I am required to retain a bill of sale that has gun make and model, SN, and buyer and seller signature, correct. Obviously it will go to an FFL if not face to face.

The upper receivers, I do not have to retain any receipt besides maybe the email correspondence for my personal records. It requires no transfer and is up to buyer to know their local laws and refs, correct?

Yes you are correct on the uppers.If you sell a gun in IL,you must run the buyer's FOID on the ILSP website for a check number and keep the info for at least ten years.I think all the info is on the ILSP website for this.For out of state,you must ship to a FFL.Good luck on your sales!