Long-recoil semi-automatic bullpup .50-caliber rifle. Big boom. https://www.youtube.com/watch?v=kf8cNeOStBI
Owing to its odd configuration, it would probably have to use the Thanatos reload animation.

Also a bit of a rare beast, only shows up in about three games; CoD:AW, Far Cry 4 and Arma 3. Only honest model download I can find is from FC4, here: https://facepunch.com/showthread.php?t=1514635&p=50141694

The download link includes the other FC4 sniper rifles; http://www.mediafire.com/file/ekd4eamk4vgr50h/FC4_Sniper.rar

As ever, any consideration and effort is extremely appreciated. The modding community has already done so much for this game and its players.