Which BBs to use with airsoft sniper rifle?

I think it's best if you experiment. You never know, .43g might actually work best for you. Madbull seems to really know their stuff when it comes to this and their .43 is the heaviest BB weight that I know of. You might want to get an even tighter barrel if you do to squeeze out more accuracy. So long as you keep your barrel clean and only use high quality BBs, they won't jam.