Like any disposition, a licensee has 7 days (478.125(e)) to enter the disposition of destroyed items.
ATF has provided clear instructions that the preferred method of destruction of a receiver or frame should be by cutting with a torch or blade in 3 places, melting in a furnace, or smashing (if it truly compacts the receiver or frame).
When a firearm is destroyed there is no provision in the statue, regulations or rulings that require a photograph be taken of the destroyed firearm. However, FFLGuard recommends taking pictures and saving them.
For more information consult the FFLGuard Help Desk