The latest results of experimental investigations of an X-band gyro-TWA using a cusp gun and a helically corrugated interaction region are presented. Results will be presented from two experimental investigations, one using a 150 kV, 35 A beam from a cold field emission cusp gun and one with a 150 kV, 70 A beam from a thermionic cusp gun. Designs for a gridded thermionic cusp gun currently under construction will also be presented. Numerical investigations of the gyro-TWA have been completed and used to predict the saturated and small signal gain of several gyro-TWA devices. These predictions are compared with the experimental results obtained.