I posted this in a discussion on another forum before, but it may be of some interest to the members here too. You find the original discussion on the German Gun Collectors Association forum
http://www.germanguns.com/upload/showthr...-Rifle-(c-1912)
In 1896 the German army conducted some tests for a replacement for the M88 "Commission" military rifle that led to the ultimate adoption of the Mauser 98 action. A total of about 2000 experimental rifles were made by Mauser, Oberndorf, for various experimental cartridges from 6 to 8 mm. After the end of these tests Mauser took back the rifles, dismantled them and sold the actions to gunmakers. Here I am concerned with the virtually unknown first version of these experimental rifles. These are small ring standard length actions, still cocking on closing like the Swedish miltary M94/96 action. Improvements over the Swedes are: They already have the reinforcing collar inside the receiver ring, the third safety locking lug and the gas flange on the bolt sleeve. I call them "pre-transitional", as they are another step in the evolution that led to the 1898 action.
Both the pre-transitional and transitional actions are so rare that nearly nobody knows them. In fact, neither Lud Olson nor Jon Speed had ever seen a real cock on closing pre-transitional action until I showed them one, borrowed each time from a fellow forester. Lud visited me in 1992, and I just retrieved Jon's date 2001 in his "Mauser Archive" book, page 25. Other "authorities" on Mausers like de Haas, Ball, Walter don't even mention these actions. Some old German gun catalogs give sparse hints only to their existence: Oscar Will, Venus-Waffenwerke in Zella, 1902/3, offered two typical "Suhl" Mauser sporters, calling them Mod.97 at Mark 96.- and Mod.99 at Mark 100.-, "Mod. 97 cocks on closing, Mod.99 cocks on opening!" Burgsmueller, Kreiensen, 1910: "Newest Mauser cliploading repeating hunting rifles, Modell 98/99 respective 1902. The locks of these new repeaters cock on opening, not to be confused with older rifles Modell 97, which cock on closing." That's all I have found so far.
As a member of another forum doubted a standard length M98 bolt may be used in these receivers, I took a new series of photos.
The complete rifle is not intresting, as it was restocked and rebarreled, likely several times during the past century, now 7x57. It's still a working hunting rifle and probably been so for several generations. The action and bolt are the incredibly low Mauser commercial serial number 17 under receiver ring, on rear wall of the magazine and on other parts. It is a standard length action. The set trigger is of the Mauser commercial type, integral with the bottom metal, without a separate aftermarket housing.
Here are two pics with the original, cock on closing bolt, cocked:

And here it is with a WW2 vintage Kar 98K bolt. As you see, it fits the receiver as well as the original one.