[ACCL]

Ok so heres the problem: when I try to shoot it the mechbox just seizes up or the piston will move half way before getting stuck.

I have opened it and every part is in order and nothing is cracked and/or broken. Funny thing is if i put everything back together without the spring, the gears and everything else will spin freely like its suppose to. I think it might be the spring but its only a M120 and im using the blue JG motor i took out of my other gun (that other gun has a M130 spring installed so like what gives?). I even tried hooking up my 9.6V battery to it but its the same.....

So does anyone have any ideas? I really dont think its my motor since it works fine in my other gun. But this time im pulling a weaker spring.....