So today i finally unlocked the GOL Magnum after 3 days and just thought i would give you guys some tips i found.
1) Don't try on Caspian Border the tower gets destroyed in minutes.
2) Use Firestorm tower, and don't go above 2nd tier or you can get burned.
3) Play capture the flag, this is what i did it on no one bothers with the tower really.
4) The kills can be with any weapon, i got 2 kills with a smaw.
5) Remember you need a sniper ribbon as i forgot this a few times

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Its worth doing the gun is real nice and has the quickest reload time and not bad velocity.