Halo 3 Security/Katana?

[Dylan]

Hey, I have 1000 GS in Halo 3. but only about 45 total achievements. People have been saying that you only need the 1000GS, but i still don't have it. Any help or advice would be greatly appreciated. BTW my gamertag is Tha Meast 13
Ok thanks that makes more sense! That website really helped! Is there any quick and easy way to get these achievements?
One more thing. i have seen people with security/katana and they only completed the campaign on normal. so do i have to do the campaign on legendary? or not?

 

[Alex]

To get the Security and Katana armor, you need to get all of the original 49 achievements. Bungie added a few new achievements having to do with the Legendary and Mythic map packs, but those achievements don't count for the Katana and Security.

Here's a link to the list of the original 49--
http://xbox360.ign.com/articles/797/797773p1.html