this one looks pretty good compared to your other stuff. maybe it's the white background (not sure why you aa'd to fit it). animation looks nice, the large gun looks rather flat though. maybe submit it to the WIP forum, get some feedback, and resubmit once it's been improved a bit?
your goal shouldn't  be to make something just good enough to get accepted, but to make something that's the best you're capable of creating, something to be proud of.
i still think this shows a good deal of improvement over your earlier work- maybe it just got low scores in the queue- i personally didn't send it back so i can't say what the actual reason was. either way, i'd advise taking advantage of the critique offered in the WIP forum.