If you are building a rifle, and the intent is to have the action engraved, would you do the heat treating before or after engraving? I don't know much about heat treating requirements of rifle actions, just curious.

After and the engraver will thank you.

The action may need to be softened for the engraver to begin with.

Not knowing much about what the engraver would like, Rifle actions are not that hard and can be engraved after the fact,

Many a custom rifle built on a factory action are embellished without any further heat treat.

So it depends on the action, the engraver, and how good of a heat treater you have. I would personally be deathly afraid to put an engraved action in the oven.

It depends on the steel you are using; for chrome moly steel (4000 series), it does not get too hard to engrave. Conversely, if you are using a low carbon steel which will be case hardened, then it might be. Depends.