sold my taurus yesterday...

what I did was basically did your normal bill of sale and also added that "I give up all rights and responsibilities to new owner" and the price I sold it for, listed everything that came with the pistol, and then the serial number.

ie:

1 - 9mm Taurus PT111 MIL PRO + S/N
2 - 12 Rnd Magazines
1 - Speed Loader
1 - Case
1 - Holster

make two copies, have both parties print + sign both so that you can have original signatures and you can have a witness if you like