GGO is an RPG, though. Spend some points in strength, and 15 kg is probably nothing serious.
In reality, and in simulation games like Arma, a rifle can have a secondary sight, such as a red dot, to use when aiming close. Here's a link to a random article featuring one such solution. However, since GGO is a shooter-RPG, I suppose it's beyond its meager ambition to feature such. Considering the numerous disadvantages a sniper rifle offers in close range, I don't really understand why, but then again, I don't really play shooter games.