Ballistically, there is no advantage to a longer barrel. The powder in a target load is all burned in the first inch or two of shot travel and the pressure peaks very early as well. So beyond the first few inches, the rest of the barrel is of no ballistic benefit.
If your mechanics are good, you should shoot as well with a 22" turkey barrel as you would with a 34" trap gun. Barrel length is all about personal preference. Trap shooters like a long sighting plane and because there's little movement of the gun between the ready position and the target break, a 34" can be an advantage. That extra length (weight) would be a liability when trying to break doubles on the skeet range or trying to pick up a fast rabbit/teal true pair.
I personally have 28" and 30" o/u's and I'm primarily a sporting shooter. The 30" is actally lighter and a faster swinging gun than the 28", so it will just depend on the gun. I like the shorter barrels for hunting, so my next gun will be a 26" o/u of some sort that will allow me to use the same gun for sporting and rabbits.
So, the answer is yes, 26" would be fine for sporting, but there are few sporting clays guns in that length. Get what feels/balances/swings well for you and learn to shoot it well.
Why is Trap in the subject but SC in the text? Do you know why YOU want an O/U over a semi? Or are you being told that?I have been told that 30" barrels are recommended for trap, but am not sure what length is good for sporting clays. I am looking to purchase an o/u for the purpose of sporting clays. Would 26" barrels be adequate?
Also, on my ported guns I often see sparks fly out the ports - thus the charge is not completely fried in the first few inches
I disagree with you at least in part - With a longer barrel you get a longer sight plane and if you use it right your accuracy will improve and so will your scores as long as you are able to swing it and maintain control.
"D-Class, 20 yard All-Americans."
I have to use this one )