The Sniper Elite V2 'Kill Hitler' DLC was at first only available to those who pre-ordered the game, and for free. If you missed out but are still interested, that content plus two rifles is now available to buy for $7.99 / 800 points on Steam / Xbox LIVE (and I assume PSN as well).
The two rifles included are the SVT-40, a Soviet semi-auto, and the Kar 98, a standard German service rifle. The SVT is a "brute" weapon with considerable bullet drop, while the Kar features extensive zoom.
Hit the trailer below for a peek, and your source of choice for the content.