Generally, the term "solder" is used when the joining metal is a lead-tin alloy, with a melting point at or under about 400 degrees Fahrenheit. Silver solder is a silver-tin alloy with a higher melting point; it makes a stronger joint, but is generally used in applications like fresh water plumbing, where the use of lead would be hazardous to persons drinking the water.
While the term brazing is sometimes used to include silver solder, the word itself comes from the use of brass and it is usually used when the bonding metal is brass or copper.
In the case of the Remington bolt not only is the handle held on by induction brazing, the front of the bolt is a separate part with both locking lugs and it is held into the bolt body by induction brazing. (NOTE: I did NOT say the bolt lugs are brazed on; that silly story was circulated by competitors when Remington first made built-up bolts. The whole front of the bolt, a part that includes the bolt face and both lugs, is inserted into the bolt body and brazed in.)
The brazing is done by electric induction; the copper is inserted between the parts, then the bolt put inside an electric coil that melts the copper and bonds the parts. The bolt handle is then tested in a machine and a punch mark used to indicate that it passed the test.
Have any Remington bolt handles ever come off? Probably there have been some, at least at first. But like many other stories, sensationalism will usually spread faster than truth. Like S&W internal locks (millions died when their guns locked up!!), M1 rifle operating rods (tens of thousands of GI's killed!!), Colt Single Actions (blew up by the thousands!!), P.38's (made of cheap stamped tin!!), such nonsense is best ignored.
Jim