In the Republic of Ireland, Reg was now the agent for NSU and Honda. From 1953 to 1955, Armstrong rode successfully for Gilera and NSU. In 1953 he came second on a Gilera in the 500 cc class, and second in the 250 cc class on an NSU. In the 1954 he came fifth on a Gilera in the 500 cc class, and ninth in the 250 cc class on an NSU. In 1955 he came second on a Gilera in the 500 cc class. In the 1956 Grand Prix motorcycle racing season he came fifth on a Gilera in the 500 cc class, but growing business interests demanded more of his time and he announced his retirement from motorcycle racing.