Help with cqb airsoft guns?

I have been looking for a cqb rifle for a while now. I am more of an echo1 fan more then anything else my max payment for the cqb gun is $250. I want rails, adjustable stock, and battery included. I am looking to add this on my back when in the field so i need it rather light weight. I will be carrying a mauser sr pro tactical sniper rifle and a ksc glock 18c with me and all acu with a tactical vest any i will take guns from other companies as well as long as they are in my price range. I am looking for a low fps like 330-390 and a fast rof. Perferably above 20 per second. Thanks for the help!