To add to the list of items for your 4457 form I would put all camera gear, binoculars, and anything else that has a serial number on it.
The few times that I have crossed the US border with my hunting gear the only time that I had to show my rifle or anything else was when I came back from Africa. When I returned from Canada all the agent asked was if my rifle was the same one that was on the 4457.
But all it takes is one that is having a bad day when you step up to them to make your day miserable.