Beautiful bird and a great picture Guy.
We don't have these birds here but we do have Red Tailed hawks.
I truly appreciate all the birds of prey.
JD338
Think of your 19" barreled 280 Remington as a 7-08. Don't worry about the speed, there's a lot of 7-08 shooters killing deer and elk at 400-500 yards with the right bullet in the right spot.
Hodgdon has powder...
https://shop.hodgdon.com/hodgdon-h4350/
https://shop.hodgdon.com/imr-4350/
JD338
I think Grand would be too slow for optimum results, especially with the shorter barrel.
Someone mentioned IMR4064 and that might not be a bad choice in a 19" barrel.
JD338
FWIW, I get discoloration when I aneal my brass. When I clean the brass in the Frankfort Arsenal wet tumbler, they come out clean and look like new brass.
JD338