2nd tier unlocks will only come if you have special forces expansion.
Once you play SF for awhile you will get retroactive unlocks to match your global score/rank, provided you have already unlocked the vanilla "tier 1" unlocks the SF unlocks will then become available.
So you want new pretty little models of different guns for your game, you have to buy Special Forces to get them. OR, borrow the SF disc from somebody you know, log into SF for awhile to play a couple rounds until you qualify to get the SF unlocks. Then never play SF again, like 1/2 of us who have SF have done.
I suggest borrowing SF isntead of buying it. Don't reward EA for their bullshit where they are forcing people to pay for additional content that used to come from 3rd party modders, modders were killed off thanks to the ranked server bullshit.