This rifle is a Steyr M95 straight-pull carbine that has been converted into a semiauto by adding a gas piston under the barrel connected to the bolt carrier, and an extension to the stock and receiver for the bolt to travel in. The pistol grip was added so that the trigger group could remain unchanged despite the longer receiver. It still feeds from the same 5-round Mannlicher clips as the standard M95, and appears to be in 8x50R (ie, not updated to the 8x56R cartridge).
This rifle is in the collection of the Beretta factory museum in Gardone val Trompia, but I have no information on whether they did the conversion themselves or acquired it elsewhere. Unfortunately, the bolt and piston mechanism is very sticky, and I was unable to disassemble it. However, it appears to be a quite simple conversion, as these sorts of things go. Just the project for the hobbyist gunsmith with a cheap extra M95 carbine and lots of spare time...
Thanks to Beretta for allowing me to have a look at this very neat rifle!