This will come in time, as it's hard to avoid getting rifle kills in Sniper Elite, what with it being a sniper game and all.
If you don't have the DLC weapons, I recommend either the Carcano or the Springfield. Both are powerful, balanced rifles. Of the two I prefer the Carcano, but the Springfield has easier to unlock upgrades. My favorite rifle overall is the extremely OP silenced De Lisle from the Silent Weapons Warfare DLC pack. However, it is very weak, even after getting the (not easy to unlock) damage upgrade.