They were suppose to build a 5 mm on the Tracker frame and a 223 on the frame they built their 500 Smith on. As far as I know they never came to market. Smith was also rumored to be working on a 223 revolver and it never happened? I was not a 5 mm fan but have a Tracker in 17 HMR and thought one in 5 mm would be a good critter gun.