Shotgun barrel length and velocity

Is the effect of barrel length on velocity in shotguns less marked than for rifles?

I reload steel duck loads with Alliant Steel Powder and am now using a 26' barrel. Steel is supposed to be a slow burning powder.

Would I get an appreciable increase in velocity if I went to a 30' barrel?

Kirill Sapelkin

No. Shotguns reach 98%+ velocity before the charge goes 20 inches down the barrel. There will be more variation in a box of shells than the minute gain that may or may not show up on a chronograph that you will get from a 30' barrel. The real advantage with a 30' barrel is the increased sight plane that many say helps with long passing shots.