Gamst joined the family business as a partner in 1811 and became its sole owner in 1829. In 1836 the name of the company was changed to H. Gamst & H. C. Lund when Gamst's nephewHans Christian Lund became a partner. In 1854, it was taken over by P. J. Winstrup and V. C. Gamél. In 1872, it was taken over by Johannes Henrik Hellerung and J. C. Hauberg.
Property
Upon selling his company in 1854, Gamst purchased Vedbygård at Holbæk.