Not familiar with the one shot rivet guns. However, you can adjust the regulator down far enough on the rivet guns I do use, then simply hit the pedal for a single hit. Reducing the pressure does reduce the force of the hit and the beats per minute - but if you went with a large rivet gun, I think it would still hit plenty hard for soft metals.
Expert on the rivet gun type machines is Kent White at
www.tinmantech.com