just letting people know this worked still as of july 11 2011. i had lost all my save data for all my games on my hard drive so i just started a new game on regular easy. going through i got all the other achieves for the dlc as i had the original 1k already and then beat the game and got the bad ending. i then followed the steps in the first post but instead of exiting to the main menu then starting i exited to the main menu then quit to dashboard and then reloaded the game and followed the steps and got both ranger achieves.
thanks OP. just figured id let people know it still worked :
i was scared that it might not then i would of ended up doing 3 runs instead of the 1 lol. enjoy!!
nothing to see here!! move along!