Barrel length for 54r

[Purdune]

Howdy All,
Wondering what the barrel length is best for the 7.62x54r round. My question stems from looking at VEPR's in 54r with different barrel lengths but the Mosin also comes to mind. Accuracy is the main factor I'm looking at. I'm guessing this might change at what range your firing at? Just curious as the Mosin is 28" and most PSL/Tiger's are 27". I see a lot of people that modify the Mosin go for a 20" and the VEPR and other Tiger copies are 20.5" and 23". It's my understanding that longer barrels flex in a wave while the bullet travels down the barrel. So I'm also guessing barrel length also depends on how thick the barrel is.

So if you wanted a 2 or 3 MOA what would you go for? Does length only matter or are there other factors with the barrel. I realize the rifle has many factors besides the barrel like whether it's semi or bolt but I'm focused on the barrel length. If you bought a VEPR and you wanted accuracy is there a big difference between the 23" and 20.5"? Is the 27" just for show/looks?