To get the security helmet you need to have over 1000 gamer scorer from halo and 50 achievements.
You can unlock the security shoulders by getting 700-850 gs (gamerscore). For the helmet you have to get 1000 gs. Now there is no security chest plate.
No you cannot buy halo 3 helmets in the game... but you can buy nerdy plastic helmets at like Gamestop...
you have to unlock achievements
you must have several achievements from HALO 3 and HALO ODST. Along with certain achievements from HALO REACH. Then you will unlock the two helmets
You have to get 1,000 gamer score on Halo 3.
You have to get certain achievements that unlock certain armor permutations.
There are no Halo 3 helmet unlocks on easy. You will either have to beat the whole campaign on normal to get the E.V.A helmet or Legendary to get some elite helmet. You can also unlock the helmets with a friend on Xbox LIVE if you are afraid that you cant do it by yourself.
No all 1000 need to be on halo 3
Technically speaking, all the helmets in the armory are Spartan helmets. If you mean the specific helmet worn by Master Cheif in Halo 3, the MJOLNIR MK. VI, then that costs 300,000 credits.
you have to get 49+ acheivments
you have to get 49+ acheivments
no
To get security armor in Halo 3... all you have to do is get all of the original 49 achievements (you don't need the new mythic or legendary achievements).