Get an old Anschutz 54....they are great guns, very accurate, and relatively cheap since they are old. Mine still drives tacks, and I have had mine for years, and it was well worn when I got it. You can probably get one in good condition for less than 600 dollars.
If you just want a decent target rifle and aren't planning on competing, an Anschutz 64 is another choice. It is lighter and cheaper than the 54, and is a great entry level rifle. It should be cheaper still, maybe 3-400 dollars?
I wouldn't get a biathalon rifle since it has a magazine.....magazines only cause problems when you are trying to shoot for pure accuracy. Also, biathalon rifles are not designed purely for target shooting....they have to be hauled all over the place so they are made very light.