It all depends on the model.
No, Never.
Which model? All the different models are assembled differently.
If its a BB Gun, Then Yes.
The reverse of how you took it apart. I would look on the web to try to find drawings of how to assemble the BB gun. Try looking at the company that made the BB gun first, some offer drawings of the gun and how to assemble it. www.Crosman.com offer this for most of their guns. OR you can take it to an Airgun repair shop to heve it re-assembled. Check "Airgun repair" on the Net and find a shop close to you.
BB gun. Fires a round BB.
Which model, what is the condition of the BB gun or is it a BB rifle..
Benjamin Breckinridge Warfield did not invent the BB gun.
A BB gun is a gun which shoots BB-size pellets, typically with the use of compressed air, or a compressed spring.
It's a BB Gun.
You don't magnetize the BB's. The Magnet is inside the BB gun. The gun has to be taken apart and the magnet that holds the BB's replaced. Not all designs use this method of holding BB in place.
You can mail a BB gun via UPS.
This BB gun was made by WHO?