Sandcast silver.

[LRB]

Ferrous metals (iron, steel) should be bent when a black-red hot. If you try that with brass, german silver, or silver, the piece will break. With those metals heat then dunk in water to anneal them-they will bend easier after that treatment. Anneal frequently as you work because they will work-harden and get brittle again.

You could fill the hole with a solder, but it will show as the triggerguard ages and gets a patina. Contact your supplier and see if you can get one without casting flaws.

There is no need to water quench non-ferrous metals. Air cooling is all that is needed but quenching will allow you to handle the piece sooner.