For ease of brass 6x45 or 6x6.8
I have both and run them to 700 yards on steel, p-dogs, coyote & antelope.
The 6x6.8 runs at starting 243 speeds with 10g less powder, very efficient caliber.
6x45 w 55/65g bullets are not to be overlooked...perfect for every varmint.
Dies are readily available & easy to get and