Do pardon me; for not mentioning the troubleshooting methods I went through before going to a airsoft retailer to get it repaired and etc. But I'll gladly list what I did in the meantime right down below.
- As lurkingknight asked me; I did try to feed it with one bb upside down manually and there was still a dry fire up top 3 times and then it shoots (2seconds as interval to every trigger pull)
- I have two kinds of magazine; one that came with the gun which is a high cap wheeling thing (LOL sorry i'm not sure how to call it) and a high cap Flash mag which is a string to be pulled and it feeds the whole mags. But both mags are fine before anything they are feeding correctly. Even pressing on it against the m4 (inserted) and same results with the dry firing.
- Jamming rod! used it and nothing was within the barrel and such
- and now about he grip I have had to change; the process on removing the original grip and motor was fine and smooth; as for inserting the new grip; man I had a hard time to insert it; the new grip itself was too tight to fit in directly. So I had to press on it several times onto the GB
- Battery is fully charged
- as for checking the internals; I didnt have the chance yet; went to a hardware store and bought a hex key set. The magazine release .. it didn't take a 1.3 mm and I have to go back again to the store to find if there is any smaller than this hex key
this is so far I can think of for the basic troubleshooting i'm capable of doing; as for opening up (if ever I find a a hex key any smaller than 1.3 mm) I never touched myself the internals aside the tech-guy at the airsoft retail