So, as far as the trials rifle goes, were they used in drills at a range or what purpose did they serve?
Noel, a trials rifle is a testrifle, or a prototype. It was made or modified to test new features, ammo etc...
In the early 1880's Krag made a "capsule magazine" for the Jarmann rifle. This was the first gun that would become the Krag Jørgensen rifle.
http://digitaltmuseum.no/011022699389/?query=jarmann&pos=22&count=171
In 1891, the norwegian army established a "Rifle commission" to find a new army rifle, and the best suitable cartridge. They did extencive ballistic tests with calibers ranging from 10,15mm to 5mm, and came to the conclusion that a 6,5mm projectile would be the best. In 1892 they allready had a prototype 6,5 x 55 rimless cartridge. At the same time they were developing the Krag, and the final version was the M/1894. The swedes were at the same time adopting a mauser rifle. they also had a prototype cartridge, and had accepted the 6,5mm caliber from the norwegian trials. In November 1893, a commission of three swedish and three norwegian officers came together and drew up the final version of the well known 6,5x55 cartridge. Norway and Sweden were in a union with the same king back then, so the plan was to have a common cartridge.
Here's some trial rifles from that time.
7x57mm Krag
http://digitaltmuseum.no/011022699394/?query=krag&page=4&pos=81&count=1309
6,5x55 mm Krag from 1892
http://digitaltmuseum.no/011022699407/?query=krag prøvegevær&pos=4&count=37
Jarmann M/1892 in 6,5x55. The label on the ammo says: "Speedloader or cartridgeholder for 6,5mm Jarmanns rifle of 1892".
http://digitaltmuseum.no/011022700246/?query=jarmann&page=2&pos=45&count=171
http://digitaltmuseum.no/011022715826/?query=patroner&page=7&pos=153&count=612
As for ammo. The original cartridge had a 156 grain roundnosed bullet (B projektil), but in 1925 the army adopted a 139 grain boattailed spitzer bullet (D projektil). The rear sight on your Krag is modified for the new bullet. With the old bullet, the ramp on the rear sight were taller than the ladder, but on yours the ramp is level with the ladder. All military Krags got this update. Todays factory ammo for Krag has a 144 grain bullet with the speed of 770 m/s. The working preasure is 40600 PSI. I have just made some handloads for my Krag, but I haven't been at the range yet. I don't shoot it much, so I have only shot factory ammo so far, but kept the brass.
PS: I have a rotten / trashed sling I don't need. You can at least reuse the metal pieces. PM me for details.