Firstly, wrong place to post, post in Gas Guns for future reference.
Secondly, you need to set the hop up, this involves taking the slide off, and adjusting a little wheel to get the most out of the gun.
Search on Youtube for WE Glock hop up adjustment, and it'll show you a step by step.
Also, you don't say with what weight BB, but I wouldn't recommend using anything under .25g for maximum range.