The Ultrastar is an interesting series, which may have pointed the way to the future of Star had it not ceased to exist. While notable as their first plastic-framed pistol, read on to see that this is not the original design intent. Also, model numbering is very unusual, in that a caliber change did not have a concordant model number change.
Presumably, this would have become a series, much as the M28/30/31 did, or perhaps as the Firestar, with additional calibers, and perhaps double-column versions. This is all speculation, however, as I have seen no other information on prototypes, and the demise of the company makes it purely an exercise in alternative history.
I do not have manuals for every pistol shown on this site. However, in many cases there is a related manual. Partly to make the series relationships clearer, and partly to assist with speed and accuracy of updating, all manuals can be found in one place, the manuals page. All manuals available are provided as downloadable PDFs, or you may purchase a printed copy of the entire set of handgun manuals.
Also using the same operating method as the M31, but with an ejector port locking block, the Ultrastar pistols are smaller and lighter guns for carry and concealment. A single-column pistol in either 9 mm Parabellum or .40 S&W cal., their primary feature of interest is a polymer frame. This is constructed with steel inserts and a ribbed magazine well for extra stiffness and strength. Fitted with a straight barrel instead of a cone, the Ultrastars are lightweight and well-suited for their intended role, with even the safety lever designed fit flush when on 'fire.'
Ultrastars are also single-column pistols, which is unusual for a newly-deisgned pistol these days, and helps make the gun slim and comfortable. They could have been designed even more slim, but instead there is significant thickness, with reinforcing webs, under each grip area. This gives the frame a very solid feel, something lacking in many other plastic framed pistols.
The Ultrastars firing pin/safety system is substantially that of the M28/30/31. The safety lever is arranged opposite that of other modern Star pistols (protruding to the rear of the axis) and is designed to fit flush when on fire, instead of sticking out like most others. The firing pin stop plate is set up as usual; depress the firing pin to slide the plate up and off. The drop safety will, of course, have to be depressed to allow enough travel in the firing pin.
The stripping pin is retained in the frame when pushed to the side to strip and is separate from the slide lock, as on the Megastar. The slide lock lever, magazine release and other features are reminiscent of the Megastar as well.
Note that there is a small stud protruding from the bottom of the butt. This looks like a lanyard loop they cut off instead of including. It makes me wonder if the pistol, in one form or another, was designed originally as a service weapon, though this is pure guesswork on my part.
The plastic framed M205 Ultrastar guns are based on a mid-1990s Model 105 with an aluminum frame and plastic grips. This alloy version apparently never reached serious production as I have never encountered nor heard of one available. It does not seem to be a prototype, as it was promoted in a limited way, appearing in firearms directories with company-distributed literature and photos. Janes's Infantry Weapons did report is as being in production in 1996, however.
Stocks are of the same style as on the Megastar, and are apparently retained by pinning action of the removable backstrap/trigger module, as on the Megastar and 28/30/31 series. Weight was reported as 810 g, whith all other features and specifications (aside from the frame construction) being identical to the later Model 205.
The references I have which refer to the Model 105 pistol make no mention of it being available in .40 S&W caliber, as it was not in existance at the time. I have surmised a .40 version as there is no reason the alloy version could not be upgraded in the same way the later model 205 was.