i would steer away from carbon fibre..too easy to pick up and hold grit.
coated is much better or polished ss
dewey or bore tech..ivey if you have money
length is end of bore guide and past the muzzle
your 6.5 may work for the 308 or the 223 may work in the 6.5,
but i would buy all three
the 223 is going to be a 22
the 6.5 is likely to be a 6mm/243
and the 308 a 30
Bookmarks