King Arms M4A1...
 

So I have a the same problem as a few people here with the King Arms...

I've had the rifle just over a week, and on the third day of firing things went sideways.

Firstly, I was losing all FPS... I'd pull the trigger, here the slap of the piston, and no BB came out.. Pulled again, same thing.... Pulled once more, POP BB flies out two feet and nose dives onto the ground.
Rinse and repeat... Every 5th or 6th BB that fired off would blast at full speed through the target...

So I decided to take matters into my own hands... The rifle was still under warranty, but I figured if I'm serious about the sport, I need to learn the internals. (I fix God damned C-17's, I figured I could handle airsoft rifles...)

I opened up the rifle, took out the hop up, and noticed the bucking was just mangled... Thought I'd found the problem... Rusty Lug nuts gave me a new bucking for the price of a coffee... Replaced it. Got the rifle put back together... Charged my battery...
Same God dang thing...

Now I've been reading about Hi Cap mags causing this issue, pistons... A lot of things... What's the problem here lads... If it's not the bucking, not the battery or motor... What's doing this!?

I'm pissed boys, I dropped 400$ so far... And it seems this is going to be a money pit with little satisfaction...

Side note: Why would a hi cap mag cause this? Doesn't make sense to me.

Might be the tappet plate. One of my friend's guns was doing doing exactly what you described a while back that after replacing the tappet plate it worked fine.

When diagnosing an airsoft rifle issue , it is helpfull to rule out as many things as possible.
Thats why people tell you to try a different mag, a different battery, different BB manufacturer etc. When you rule out as many things as possible it narrows the search considerably, Does it act the same if you hold the gun upside down?

What brand of rubber did you replace the stock one with?
What brand of BBs are you using?
Is the spring on the top of the hop up unit in place?
Try a different magazine.

1. Guarder Silicone Hop Bucking.
2. .20g Double Refined Premium 6mm Airsoft Ammo.. Velocity arms. Got it when I got the rifle.
3.Yes.
4. I ordered new mags...

I'll have to look into the tappet plate... I ordered new mags, should be here by the end of the week... I needed a few extra anyways.

I'll update as soon as the mags come...

Try holding the mag at a different angle (ie. shim it forward or backwards). I know some mags are really finnicky about how they align with the hole at the bottom of the hop up and I had to push my mag forward to get it to feed properly (shim with a piece of soft velcro on the back of the magwell and you're good to go). However that doesn't solve your shoot 3 feet then immediately drop problem. For that it might have to do with the BB hitting the edges of your flash hider. I've only seen it once with an offspec PDW flash hider but it could be... Try removing the flash hider and firing and see how the BB's behave as they exit the barrel.

Hopup turned for too much hop?
Hopup shredded?
You replaced the rubber - nozzle mating with rubber for an airtight seal?
Have you run a compression test?

one of the first tests I do is turn the rifle upside down and hand feed the BBs into the hopup with no mag. This will tell you if it will at least fire. Doing this eliminates the possibility of the mag not being perfectly placed by either not being high enough, forward/backward enough, too high, springs not pushing BBS etc.

Also turn the hopup all the way down for your testing and eliminate the possibility that it's set too high and actually blocking the BB from leaving.


when it fails to fire, is the sound any different from when it was working? Or does it just sound like a regular dry fire?

angrypanda83 If you wish i can go over to your place- with a low cap mag full of BB Bastard bb's and have a look at the gun, I have some experience with m4's

lurkingknight: when the weapon wasn't working properly, I had turned it over with no mag in it. There was a BB in the hop up, and I pulled the trigger. Bam, the bb shot out at full fps, and there was no issue... It made the right sound as when it was working.

rusty: That would be awesome, I'm working tomorrow until 3... I cut the connectors off to put on the deans... So I'll let you know when I get the wiring fixed.

Sounds like ammo or compression issue
Don't be upset, happens to a lot of new players. No airsoft gun is perfect out of the box!

Hey AngryPanda:

I just had a customer's gun this morning that did the same thing as you are describing.

The problem was loose fitting mags in the magwell. I shimmed the rear of the Magwell with 4 short pieces of high quality black electrical tape. Yours may need more or less tape. Probably not more or you wont get the mag in the well.

As a more permanent fix, try using HPDE sheets. Much longer-lasting and very low on friction.

Good ideas as usual, Stealth. But how would you get it to stick. The stuff is oil in a solid form, nothing sticks to it!