All the better brands WORK... finding one is likely a bigger part of your decision then what it is.
For general plinking, anything from 26" to 30" work. All you are doing is balancing muzzle velocity with ease of tuning. I have taken 20" rifles and sent bullets to 1450yds. It just needed more elevation.
For competition, max out on the rules, ballistics even if it is more work or costs more.
See Krieger site on their thoughts on 5R rifling.
Ask Shilen about their canted or ratchet rifling.
We are always happy to accomodate what the consumer wants..... sometimes the best answer is "Sure".
If the results stand, a new NRA SR BR rail gun group and agg record was set with a 6 groove standard lands Shilen
Jerry