I hope this is the right place to post this.

When we all bought our weapons there was paperwork done, like the background check, etc. Is there a way to get a copy of this to show actual ownership of the weapon? All I have is the receipt and it doesn't show serial number or anything. In case my AK or any of my weapons are ever stolen, lost, whatever what can I do to prove that this weapon is mine?

Another question. I sold one of my weapons to one of my friends. I know I need to write a receipt. Is there anything else I need to validate the exchange?

The records are kept at the FFL where the firearm was purchased. You could probably ask them
for a copy of the paperwork. When I do individual sells I write out a little "contract" explaining the sell that he/she is legal to own a firearm
with serial numbers and both our SSN#'s followed with signatures just to cover my ass. I don't think you have to do all of that at least not here
SC, but better safe than sorry.

I had about 20 guns stolen a couple years back, I had pictures of all of them and all the serial numbers, turned all of that into the law enforcement

about 8 months later I had 19 back (the one derringer is missing, but that could be anywhere since it is sooo small) and the perp was put behind bars, too bad he got out after 3 months, so much for our justice system

Yeah the back ground check is just that a check, the info is kept at the FFL.

If you have a digital camera and basic photo software (a normal camera will work but it takes longer), Take a good pic or two of the firearm then use the software to add info to the pic like make, model, serial #. Then put all this info on a CD/DVD and make several copies, if you have a bank box put one in there and send one or more to family or close friends to hold for you. If you sell one you can always edit the pics and add the info of the seller to it.