Born in Moston, Cheshire and based in Stoke-on-Trent, Armstrong moved into boxing from kickboxing and made his professional debut in January 1988, knocking John Hales out in the first round.
Beaten only twice in his first 15 fights, in September 1990 he challenged for Modesty Napunyi's Commonwealth featherweight title, losing in a ninth round knockout.
He won his next three fights, including a final eliminator against Darren Elsdon, setting up a challenge for John Doherty's British super featherweight title in April 1992 at the G-Mex Centre in Manchester.
He was out of the ring until May 1993, when he faced Jon Jo Irwin for the vacant WBO Penta-Continental super featherweight title, losing on points.
In May 1995 he challenged Floyd Havard for the British super featherweight title, losing by knockout in the ninth round.