Select is RS sent through a screen a few more times. I used to only shoot Select. Then like you, ran out and all they had was RS. So I shot that and never noticed a difference in accuracy or velocity.

A good load for your Hawkins and cheap to shoot is a roundball and 85 grains of RS powder under it. If your rifle is a .50 then use a .490 ball and a .015-.018 patch. If its a .54 use a .530 ball and the same patch and powder amount.