Every so often I get an email asking about the feasibility of building a multi-caliber revolver along the lines of a Phillips & Rogers Medusa. There have been several attempts to build and market such a revolver over the years, and none of them succeeded. ...Aside from the general silliness of the concept (you can't get .38 Special during the Zombie Apocalypse, but you can get 9mm Largo?!?), I've always been leery of a chamber that would handle such a wide range of dimensions and pressures. Ed Harris, of course, has first-hand experience and was able to she a lot of light on the question. ..."At that time the company was also building 9mm revolvers for the French police, and .380/200 British revolvers for India, as well with experimenting with a hybrid chamber for a government customer who wanted the ability to use 9mm Parabellum, 9mm Largo or .38 Super, with clips, or .38 Special +P without the clips. This pipe dream did not work out, because when using fast-burning powders with soft bullets, including most JHP designs for 9mm, the bullet base may upset to conform to the .379" diameter chamber mouth [editorial note: the space just prior to the chamber throat, which is exposed with shooting the shorter cartridges], resulting in a steep pressure rise of over 10,000 psi as the upset bullet base had to squeeze down again as it transitioned into the smaller diameter ball seat in the front end of the cylinder. While the result was not dangerous when firing lower powered ammunition such as .38 S&W or .380/200 British, it was more interesting with 9mm Parabellum, 9mm Federal, and .38 Super. ...Problems with case splits [when] firing .38 Special +P and +P+ when chamber enlarged enough in back to accept 9x19mm. ...Speaking of unsafe, Ed passed along information about their unauthorized experiments with the then-new 9mm Federal round, which was a 9mm rimmed cartridge made to fit the a version of the Charter Arms Pit Bull revolver. ... Anyhow, Ed tells of their fun with a "non-approved" use, and finally we have part of the answer as to why the 9mm Federal disappeared as quickly as it arrived: ...When 9mm Federal ammo arrived Roy Melcher was curious as to whether rounds would enter .38 S&W chamber and we didn't have any US made guns, so tried in the ROF No.2. ... They went on to take apart a bunch more .38 S&Ws of various makes and killed the project shortly afterward."