King Arms M4a1 fitment issues
 

I got my self a KA m4a1 yesterday

i pulled the upper receiver off so that i could add some quick disconnects for the plug for easy dis-assembly, i also removed the the dummy bolt to make work easier.

now im trying to but the upper back on and it wont seat back all the way in?

any one got the same issue?

http://i338.photobucket.com/albums/n...psd3091250.jpg

http://i338.photobucket.com/albums/n...ps600665f8.jpg

that is as close as i can get it any and all help would be greatly appreciated


i have had 2 m4s before one a tm and the other a Dboys and they all went back together no problem but this one i cant figure out

Pinch the tabs together.

which tabs are you talking about i do not see any?

Push down and back. It can be difficult because it's such a tight fit.

pretty much just brute force? is there anything that could be stopping it

Lift the charging handle slightly when you push the upper into place.

i got it i think it was design with the bare metal tolerances with out the paint a rubber mallet fixed it, i assume the more i remove it and put it back the easier it will be?

squeeze and brute force it together, just DO NOT bang anything. No hammers or hitting, just constant force. Hammering sometimes causes receivers to break
and make sure your dust cover isn't catching the front receiver pin. Sometimes they flip down and catch the pin if it's the retention type.

I second this. My KA M4 has the exact same deal.

Ya if I remember correctly, the charging handle has to be pulled twice during assembly, once to get over that little bump, and once at the very end to get it those last few mm.

I was already past the part where you need to lift the charging handle. i did notice the dust cover catching. i only had to get the back of the upper to go down about .3mm and back 1mm just so the lip got seated

i tried that and it did nothing

make sure the hop chambers all the way forward and not catching on the wiring

Make sure your hop up unit is sitting in place properly too - squeeze that top receiver at the ass end and push down and in at the same time.

This fitment issue is standard on Colt KA M4a1's - my neighbors are probably firm believers that I have tourettes with the amount of swearing I did when I was first discovering this.

The charging handle also has to get over a hump on the gearbox as well so watch out for that.

thanks the hop up was all the way in, i did try wrestling with it using all my body weight but it wouldnt go down, i can see why your neighbors would think that lol its a pain, and i was able to negotiate the bump on the gearbox, it was pretty standard on most m4s

There are 2 things that stop the KA receiver from going that last 1.5mm.

1) What Stealth Alluded to, you need to "pinch" the upper receiver near the back so that the tabs will slide into the lower. Just use your fingers for this, not vise grips. These receivers are brittle.

2) The gearbox has to line up properly with the hopup so that the hopup kind of goes into the front of the gearbox a little bit.