From the Trapshooting Hall of Fame, the winner of the 1930 Grand American Handicap was Alfred Rufus King of Wichita Falls, Texas.
The 1930, 1931, 1932 and 50-F (likely 1933) Ithaca catalogues all list five GAH winners in 12 years with Ithacas -- Mose Newman (1929), Charles Young (1926), Elmer Starner (1925), John Henry (1918), and Charles Larson (1917). Four are shown with Ithaca SBTs and Mose Newman isn't shown with a gun. Ithaca Catalogue No. 51-F (likely 1934) adds A.E. Sheffield (1932) shown holding a Grade 5E SBT. The next Ithaca catalogue No. 54 (1935) adds L.G. Dana (1934) also shown holding a Grade 5E SBT. The 1938 Ithaca catalogue adds Frank G. Carroll (1937) shown holding a Victory Grade. The 1940 Ithaca catalogue adds D.L. Ritchie (1939) holding an SBT, and uses a different picture of Mose Newman, this time holding an SBT. No changes for the 1942 Ithaca catalogue, but by the 1947 Ithaca catalogue they added J.F. Holderman (1942) and Don Englebry (1945), again both holding SBTs. So, if anyone won at the GAH with a NID, Ithaca didn't capitalize on it and I'd sure think they would.
