New, small airsoft gun?

New 170$ airsoft gun shooting wierd please help!!?

• i have a cyma m5, this gun right here. http://www.airsoftmegastore.com/CYMA_Full_Metal_M5_A4_RAS_AEG_Rifle_Full_Stock_p/cyma-cm041b.htm and its 2 days old and i bbs come out far and accurate and then all of a sudden a few will only go a few feet and like lob out of the barrel and then it will go back to shooting fine. also today i noticed that in full auto it will shoot a few good then a few completey off target then a few lob out then a few really good ones again. I HAVE NO IDEA WHAT THIS COULD BE. i was thinking barrel is dirty or needs to be lubed but no, i was also thinking it has something to do with the hop up system. I contacted airsoft mega store when i first got it complaing how the gun looked used because it had a few white marks on it and a scratch and he said that hes sure there not used only a few are test fired to make sure they work. i also noticed they have a 45 day garuentee fo there guns but you have to pay for the shipping there and back?!?! is that legal, if they sell me a gun that obviously isnt soppose to do what it says and i have to pay for it to go there and back for them to fix it and not even give me a new one! someone please tell me what you think i should do, there closed until tomorrow and i just wana get an idea of what i should do thanks!!!

• Answer:

  Try cleaning then lubbing up the barel or check the hop-up and look up YouTube videos