Airsoft Canada - View Single Post - Why your KA M4 doesn't assemble properly.

Spike · March 18th, 2013, 22:02

After seeing this issue for the millionth time, I decided to go over every millimeter of a king arms M4 that wouldn't close. I found the culprit.

As you probably know already, the lower receiver pins/screws have to go in a stupidly specific order. The part that actually catches and prevents the receivers from mating is the hop up unit. The gearbox sits angled slightly downwards, so the top of the hop up unit hits the top of the gearbox shell and misses the hole ever so slightly, so the receiver can't go any farther forward.

Also, if you find yourself with a surprisingly low FPS after reassembly, take out the buffer tube main screw and the pistol grip screws and replace them with just enough torque to stay put. This will hopefully fix the gearbox's angle and will fix the FPS issue.

Just thought I'd share this, I know it's given me a headache in the past. I'd take a picture, but I'm not taking this damn thing apart again.

March 18th, 2013, 22:02	#1
Spike Privateer Airsoft Trader rating Join Date: Dec 2008 Location: Beaverbank, NS	Why your KA M4 doesn't assemble properly. After seeing this issue for the millionth time, I decided to go over every millimeter of a king arms M4 that wouldn't close. I found the culprit. As you probably know already, the lower receiver pins/screws have to go in a stupidly specific order. The part that actually catches and prevents the receivers from mating is the hop up unit. The gearbox sits angled slightly downwards, so the top of the hop up unit hits the top of the gearbox shell and misses the hole ever so slightly, so the receiver can't go any farther forward. Also, if you find yourself with a surprisingly low FPS after reassembly, take out the buffer tube main screw and the pistol grip screws and replace them with just enough torque to stay put. This will hopefully fix the gearbox's angle and will fix the FPS issue. Just thought I'd share this, I know it's given me a headache in the past. I'd take a picture, but I'm not taking this damn thing apart again. __________________ I change primaries like other people change socks.