The 243 will do a great job if you place your shot in the right place. The only copper bullets out there are the Barnes TTSX and TSX (they are essentially the same thing but the TTSX has a plastic tip), the Nosler E-Tip, the Hornady GMX, and the Remington Lead-Free (which is actually a GMX in a new wrapper).
All will do the job you are looking for. They won't be 100 grains but with the weight retention that copper bullets have they will still preform great if not better then what you are used to. I would go Hornady GMX Superperformance and see if my rifle likes them.

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