Title sums it up pretty much, This cheat in the video shown will allow you to select your level and chapter.
Step 1 : New Save
Step 2 : Pick a Difficulty not yet completed i.e INSANE mode.
Step 3 : Stand between the two little rocks in the water when the game begins.
Step 4: Press and hold LB+LT+RB+RT+A for a few seconds until you hear a sound and keep holding till the sound stops.
Step 5: Go to the options menu, select gun, go to missions, chose main, then magruders mine, load it, go back to the gun option and chose checkpoints and then kill magruder part 2, finish him and finally get your achievement.
-REPEAT
I used to be on the achieve360points forum alot, stumbled across when looking for info on the game before buying, hell of a time saver it was
.
Video - This video is showing you how to get back to the begining after finishing the game to then use the cheat, however you can just begin a new save and do whats listed above.
Enjoy the achievements!!
Extra: GOLD LOCATIONS VIDEO!!
http://video.google.co.uk/videoplay?...835&q=gun+gold 
Linear Mode
