I wouldn't say that most are from 26" barrels. The reloading manual should tell you what the test rifle was and the barrel length. In my personal experience I have seen some that lost as much as 100fps per inch, and some that lost as little as 50fps per inch. The question is how much difference will you notice. Out to 300 yards you will probably not ever be able to tell a difference.
Ted, How's things going down in Grady county?