If your on a budget the BAR10, if you want something thats good to start from and then upgrade the VSR, and if you fancy a challenge getting everything set just right and like taking your guns apart and tinkering with them, the Maruzen.
The most adaptable/Upgradable, that is easy and cheap to do is the VSR G-Spec.
The most adaptable/Upgradable, that is easy and cheap to do is the VSR G-Spec.