Considering that the difference between a 28" and 20" barrel with a 150gr bullet in .308, as an example, might be 200fps, what does barrel length have to do with distance?
If you know it's 500 yards, a 200fps difference might be a couple clicks, if you don't know it's 500 yards, the 200fps is not going to help your guess.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.