Standard GI type sights and light sights like that on the Norinco should stay on just fine with staking. There is no need for silver solder or any other method of fastening.
High and heavy steel target sights are another story. With heavy loads or lots of use, the inertia of the sight tends to cause the sight to break at the tenon or come loose under recoil. Silver solder won't prevent this, since the tenon breaks above the solder. The only solution is to make sure the tenon is wide and thick enough to stay in one piece when staked, or go to a dovetail type sight. (No, Loctite won't do the job either; it won't hold even a light sight in place, let alone a heavy one.)
Jim