I am currently working on this achievement so decided to put together a spreadsheet for people (and myself) to use in order to keep track of progress towards all the Survival Armories Achievements. As far as I can see the game only notifies you of weapons which have been unlocked for purchase, not what you HAVE purchased which is annoying.
I have uploaded this to google docs and is accessible from https://docs.google.com/spreadsheet/ccc?key=0AoS2fISiGUk8dFZ...
I have set it for public viewing and usage so you should be able to make a copy and print etc.
I have included next to the items the level which is required to unlock them for purchase and what it will cost you. These items can be unlocked in multiple playthrough's so keep at it and you will get this.
Any problems with the link or any improvements you think could be made let me know.
Hopefully this is of use to everyone. Thanks for looking. RB