http://apbdb.com/search/?q=OCA+Nano   and   http://apbdb.com/items/Weapon_Rifle_SACR/ no one will be able to give you advice as 100% to obtain rare rewards . in the old forum twice raised this question. once on Facebook. no prescription . if I am not mistaken  it was officially commented that you yourself can not affect the get of these prizes . (lottery)