I have a simple one for my meager (by ArfCom standards) supply... all my ammo is in ammo cans, so first column is Can Number, followed by: Caliber, Manufacturer, Product Name, Grain, Projectile Type, Quantity, Date of final seal/dessicant (or marked as "open" if it is a can of 'short-term' ammo) and a small empty space for written/typed notes. I keep lot numbers on my individual can labels, so I left them off the spreadsheet to save space.
Fits nicely on 4 pages, landscape format, Arial 10 font, extra line between each can.
I keep an electronic copy at home and at work, and a printed copy by the ammo fort on a clipboard so I can jot down changes.
Not worried about records. As stated, not illegal for me to own, and since most was purchased with a credit card there is already a paper trail. Hell... my "work" copy is kept on my gubmint computer.