This is a guide on how to level BMG really quick in Defiance MMO. It was recorded when the +25% weapon training bonus was on.

Forges are the best way to level up your weapon, as they have high HP, as well as, unlike as hulkers, a really high crit multiplier weak spot. This location is also great, as it does not require any access to a mission or Arkfall, and the respawn rate for it is really quick if in case your Forge dies.

It require an access to San Francisco, but if your character is not that far in story yet, just ask your friend to go to Overpass and teleport to him!