Is a 28in or 30in barrel best for pigeon shooting?
Is there any difference in ballistic performance between the two? What do you recommend?
There would be no noticeable difference in ballistic performance between a 28 and a 30in barrel on a semi-auto, and therefore it is only a matter of personal preference.
Do remember, however, that an auto has a long receiver, so a 28 points and handles like a 30-inch break-action gun.
Bearing in mind that you will be shooting from a hide, or maybe roost shooting in woodland, my preference would be for the 28.
In fact, years ago when I had a 28-inch Remington 11-87, I bought a spare 26-inch barrel for shooting from pigeon hides and in woodland.
With the short barrel fitted, the gun handled like a 28-inch break action.