The Model 2000 is a bolt action target rifle that had a biathlon kit available with a 5 round magazine. My understanding is that the biathlon kit is extremely hard to come by but the same #71902 magazines will work if converted. I'm sure some of the model 70/795 parts could be used to convert it. The ejector/mag release part may not be long enough for the model 2000 stock.
As it turns out when you remove the stock the magazine carriage and the release are all in place. There is a fake magazine installed to keep rounds from falling down into the stock. I purchased a #71902 magazine and it fits fine in the carriage, but I currently have the gun in pieces so I am not sure how it will work when it is assembled. I would like to get a picture of what one of these guns looks like from the bottom with a magazine installed. Or I would like to know what the biathlon kit consisted of. As far as I can tell everything is in place to add the magazine, but the aluminum rail on the bottom of the stock is going to need to be milled out so that the magazine can be inserted.