Is the slingshot copper alloy or 304 stainless steel?

Considering corrosion resistance and oxidation resistance, 304 stainless steel is better.

If mechanical strength is considered, both can be used, depending on personal preference.

The cost of stainless steel is lower than that of copper alloy, the mechanical strength is slightly better than that of some copper alloys (but the difference between them is not particularly far, and it is not easy to break down after being used enough), and the corrosion resistance is completely better than that of copper alloy (especially in the case of sweating, copper alloy is easy to oxidize and turn black, which will produce a copper smell, but stainless steel will not).

Of course, some high-strength bronzes are better than 304 stainless steel, but they will still be corroded by sweat. However, some people like the patina color after copper oxidation, so it depends on personal preference.

In addition, if you want to approach the color of silverware, you can consider zinc-white copper (copper-nickel-zinc alloy), which is not easy to break when used enough, and the color is closer to silver than stainless steel.