I have enough firearms (mostly centerfire rifles), that mine are described by:
manufacturer, then model, then caliber, and finally by serial number. I have the digital files and photos on various electronic media, as well as notebooks with all that information, as well as information on the accessories on the rifle including: custom or factory barrel description, length, twist rate and other information, stock mfg., type, material and LOP, scope mfg., model with serial number and description, scope mount information, ring information, trigger information including mfg., model and pull weight, zero distance, load/ammunition information including accuracy and velocity(s) with environmental inputs, and various other information pertinent to the particular firearm.
Each rifle has its own book but, I have a couple of master copies with all the firearms included. One master copy is keep in my safe deposit box, the other in my primary gun safe. My will also includes this information but, is only updated annually. I also included in the master copies and my will, who each firearm is to be left to, in the event of my demise.