I have a Remington catalog from 1976 and the Wingmaster (non-magnum model) was available with IC choke only in a 26" barrel. Modified was only available in 28". Full choke was available in 28" and 30" barrels. I suppose it streamlined production prior to the advent of choke tubes. It was similar with doubles, too. 26" barrels came IC/Mod, and 28" and longer were Mod/Full. They had less imagination back then.