What cartridge are you planning to shoot. For non magnums you really don't need a 24 inch barrel.

Thanks for the input guys I thought I had read somewhere that it was 100-200fps per inch. I am glad to know that is not the case.

6.5 creedmoor

20" is fine for hunting with the cute little Creed...

even if it was 200-300 FPS< unless you shooting WAY past 500 yards, your NOT getting a noticeable difference really
if your Match shooting every bit helps, but on a hunting rifle set up for average hunting
its splitting hairs, and NOT worth the price to add if NOT in a production set up
or NOT to me

Longer barrels can SOME TIMES help stabilize a bullet, but even that is not a huge deal here
finding a load your rifle likes and shooting it at all distances you would SHOOT at a game animal is the better way to learn and do better at distance! , than relying on a 2 inch longer barrel ever will!
shooting far is all about practice and knowing YOUR limits and the gun's in YOUR hands!

check other models... of Tikka, I believe their standard tikka length barrel is 22"

I believe they have 2 lengths on certain models/calibers.

In the 6.5 Creedmoor a 20" or 22" is plenty long enough if you are planning on using it at "normal" ranges. With the 20" barrel on the model you want the loss is less than 100 fps.