Heat deflector aka heat shield.
Not familiar with an atomic rifle. There have been artillery pieces that can fire an atomic shell, but not a rifle.
no
It will be marked on the barrel.
You need to see a gunsmith
you can't.
You need to take it to a gunsmith.
No it does not. The Browning BPS Hunter is a shotgun. The "410" signifies the shell size (guage) in this case .410
Should be marked on the barrel
From Browning's website - "allowing the shooter to retain shells in the magazine and eject a shell from the chamber without feeding from the magazine."
By pulling the trigger, by dropping it with a shell in the chamber and by a slamfire.
The Riflemans gun held 12