I traded for a Weatherby Vanguard II chambered in 223 Rem. It has a 20 inch barrel with one in 9 twist.

What kind of factory ammo or reloads have anyone used?

I want to stick with 55 - 65 grain hunting rounds, but will definitely use the 69 Grain Sierra Matchking for plinking, etc.

I just don't know where to start velocity wise. I'd like to be able to go for Whitetails and below. I have always had great accuracy @ 2600 fps with the 69 Grain Sierra Matchking, but hate to limit the effective range of the great little gun and cartridge with that.

I plan to use and would like to stick with 748 and H-335 with Sierra Gamekings but am open to suggestion bullet wise. RE-15 is another possible powder, but would like to use finer ball powder in the little case, straight from the powder measure.

You should be able to get the 69 grain bullet moving faster than 2600 fps, in fact you can get the 75 grain Hornady BTHP running that fast in your 20 inch barrel. How do you figure you would be limiting effective range? The 223 is a pretty small round and it has limitations that can't be overcome.