Jahanz probably means 3x Fire Rate Boosters, 1x Sniper Tower. That would produce both massive range and massive fire rate. My personal favourite is 1xSniper, 1xSplash, and 2xMG. Rapid Fire, High Damage, and enough Blast to seriously punish tightly packed foes.
When making a mega turret try mixing : machinegun tower, splash tower, sniper tower and firerate booster tower. U get a mega mean highpowered machinegun that deals about 700 damage per shot :D
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