KWA M4 firing but NOT hitting target
 

MY KWA M4A1 is brand new. I've had it for about a week. I shot about a good 3000 rounds so far with no problems until this morning. Heres the problem:

When I take aim and shoot, my KWA M4 hits the target alright - but 3 inches below from where I point it at. My gun is totally stock, I am currently using the stock iron sights for the front and the rear, funny thing is this never happened yesterday. I've switched onto several sights hoping to solve this aiming problem, EOTech, red dot, etc. NOTHING CHANGED, even with a different elevation and windage the same problem occurs.

I tried adjusing the hop-up it self, I rolled back on fourth and it seems the hop-up doesn't even exist. I also test fired several shots at several distances. From 10 feet to almost 50 feet - same results.

Has anybody encountered the same problem? Anybody know what is going on?
I'm guessing I need to clean the gun right? But which component? Bucking? Hop-up assembly? Something needs to be lubed?

Perhaps my hop-up broke or? I don't know. It was working fine yesterday, its like the gun just doesn't want to work this morning.

I've included a picture to show to screw up this is.
I need everyones advice. All comments are appreciated.

-Rick

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EDIT

PROBLEM SOVLED!

After hours of surfing the web for help and trial and error, I've finally decided to open up the gun myself to see what the hell is goin on. My intention was to cleaning out the barrel and hop up chamber, hoping it would fix the problem. To my surprise, after I took apart the chamber, I discovered there was no bucking!!!

For those of you who don't know a "hop-up" system features two rubber pieces, one rubber tube that covers the outside of the inner barrel and another slightly smaller rubber piece inserted into the hop up chamber, the system works by when the dial turns, it lowers and presses smaller rubber piece into the inner barrel making a lump to create the backspin. Figures why the hop up never responded.

Heres a video from youtube showing what that piece looks like,at 1:38 *THAT TINY RUBBER PIECE WAS MISSING*. YouTube - replacing the hopup on an airsoft gun

Who could have thought a non-functioning "Hop-up" was in my F%$#ing gun. For the record my all my sights were correctly.

Anyways........I'm ordering the parts in today from http://www.airsoftparts.ca/store2/. Thanks for all the help.

I've included a picture of the missing piece in my hop-up set.

Maybe simply adjust your hopup a little?

EDIT
Yes, I realize that you're hitting four inches BELOW, it you adjust your hopup a little: The bb will rise on the target.

How far away are you shooting from?

or maybe your sights are off?

I'm shooting from about 10 feet away. Should I turn the hop-up down or up?

clockwise=bullets will go up more
counterclockwise=bullets will go down more

Hopups don't usually noticibly start taking effect until after 10'.

10' is waaaaay too short a distance to be sighting guns, even pistols.

Uh, since we are on this topic, wondering what would be an ideal/good distance to sight an AEG?

Edit: in order to correctly adjust the sights/scope

70 feet is pretty good

Sorry, edited out double post.

You sight the gun at the distance you intend to be shoot at.

you are either aiming wrong or the sights are off, my kwa sights were off until I forcefull turned a few numbs into the right position.

Adjust then shoot, adjust then shoot...only way to see wtf is goin on...

you dont even have a descent gun yet don't give out adivises you don't know about.

you usually sight it in at the distance you usually engage at. 75 feet sounds about good

sights and everything were set up correctly.

Your sights are 2" above the barrel,move farther away.30'min.

no it wasnt. You have to adjust it correctly. If you have your sights zeroed for 80 feet, the shots WILL hit lower than where you aimed for if the range was less than 80 feet(Provided that the BB doesnt nose dive.)