Info on Izhmash biathlon rifle models

[thegreat]

Hello, can anyone explain the difference between the Izhmash biathlon rifle models? It seems like there are many variations based on the Bi 7 model, e.g. Basic, 7-2, 7-3, 7-4 and 7-5. Also, do you know when they were introduced, and any changes across the years? Any help appreciated.

[crasher]

7-2 is the basic rifle not set up for biathlon with covered sights or magazines holders built into the stock. It has a single stage trigger.

The only difference that I can tell between a 7-3 and a 7-4 is the stock. The stock on the 7-3 has a shorter LOP than the 7-4. The trigger(2 stage), barrel and action on appear to be the same between the two.