King Arms M4 Feeding Problems + Ammo Problems
 

I've tried some of the advice from other threads, but so far everything I've tried seems to make the problem worse.

Original Problem: My gun was not feeding, or would feed the first few shots and then would miss until I removed and reinserted the mag. Seemed to be happening on both my King Arms and MAG brand midcaps.

Last week I changed the bucking and nub with a modify flat hop hard type, and added a piece of loop Velcro to the inside of my mag well to stiffen up the mags.

Results were again hit and miss, but now I was having the added problem of double-feeding, or at least now I noticed the double-feeding...

Today I opened up my gear box, cleaned it out and re-shimmed my sector gear a bit tighter (it was loose before). I also changed the stock air nozzle with an aluminum SHS one, and put a new O-ring on the piston head.

The gun cycles fine, the nozzle oscillates and I can feel air leaving the end of my barrel, but now the gun doesn't seem to shoot anything at all?

Edit 2015-10-24: Gun is back to normal after putting back the stock nozzle. The SHS aluminum nozzle was too long, then I filed it too short which created different problems. See my chart at the end of page 2 for the problem I'm having with BB Bastard Frag Ammo feeding in certain mags.

Original issue: Try changing your hop up rubber. KA rubbers are known to be problematic.

Current issue: SHS nozzles are known to be slightly too long. File off about a 1/3 of a mm or put the stock nozzle back in.

Turn the gun upside down while the magazine is inside and try firing.

With no magazine in the gun, fill up the hopup with BB's, turn it upside down, and try firing with an unjamming rod in the feed hole to prevent them from bouncing out.

With the barrel removed, place the hop-up on the gearbox and see if the nozzle will reach at least half-way into the bb chamber, and clear or retract COMPLETELY out of the feeding hole where the bb's come up from the magazine.

First two will isolate that it is not a magazine issue, since it's still unclear if you have 1 or more unresolved issues.

The third will isolate the suspicions of a compatibility error with the nozzle.

there's your problem. shs nozzle is too long.

Also, gears are not supposed to be tight. They are supposed to have a certain amount of play on the axle.

Bad wording. The gears are not "tight". They spin freely, now with less lateral movement. Before there was a lot of side-to-side movement, it was evident in the sound of the gun when fired.

I'll try some of the mentioned tests and then maybe I'll change back the air nozzle.

Preliminary tests show that the shs nozzle is too long. I can see it peeking into the hopup chamber when retracted.

Feeding bb's by hand can be done, but I had to use my unjamming rod to push them in with more force than any magazine spring would supply.

Ill file down the nozzle as a start. Are there any negative repercussions to filing the end of the nozzle? Will it negatively affect my FPS?

Sounds like dirt mags but that's me.

Found that Dboys M4 mags and Cyma seem to feed flawlessly.

Try oiling your mag springs. Sounds like shit mags to me. If you've changed the bucking and hop up and it's still doing it then yeah the mags or it's the nozzle. The nozzle. You're using the wrong nozzle. I've done it. Took bad advise someone saying that an Mo5 nozzle and M4 are the same and they aren't even close. Only thing I can think of. If that doesn't work maybe the hop up is too close or not seated properly in the barrel.

Filed down the nozzle, it fires now. Just need to find a chrono to test the FPS, and run it for an extended period to see if it starts to double feed again.

The Nozzle I got was labelled as an M4 nozzle

every brand of nozzle is of different length. shs m4 nozzle is longer than average.

MP5 and M4 are different, however MP5K nozzles work in M4s.

As long as you have sufficient clearing when the nozzle retracts, you shouldn't have a feeding problem again. All signs/symptoms point to the nozzle. Glad you found the cause.

So I just put about 300 rounds through the gun.

My VFC Hi-cap works fine
My VFC Mid-Cap works fine
My King Arms mid-cap misfeed every 5-10 shots.
One of my MAG mid-caps misfeeds every few shots, I'll assume this is consistent with the 8 others I own...

If I recall, I only started having problems with my MAG magazines once I changed the stock handguard for an MK18 RIS. Is there any way this change could have some how thrown off the tolerance such that my MAG mags suddenly don't feed as well as they used to?!

Does the orientation of te mag make a difference? Only way your rail installation could have messed with anything is if your outer barrel is not seating correctly after you put on a new barrel nut.

Orientation of the mag? I just put the mag in and leave it. I added some velcro in the mag well to stiffen things up. Before I had some problems with mags not clicking in, especially the MAG brand. They would shuffle up and down a bit which obviously created feeding problems.

Shouldn't. As long as the barrel is sitting in the receiver as it is supposed to shouldn't be a problem. What I do is throw some silicone oil into mag and work the spring with an unjamming rod with the end cut off so it doesn't get stuck and work it that way. I only had bad feeds once. Using a G&P sentry and KWA mid caps. They fed like ass. Some mags just don't gel with some guns but like I said. The CYMA and DBoys mags always fed flawlessly for me

Update!
 

So.

I still haven't been able to fix the problem fully. I reinstalled the original nozzle, and took the recommendation of putting Velcro in the back of the mag well as opposed to the front where I had it before.

My King Arms seems to shoot fine with the King Arms high-cap that came with my gun (no miss-fires, and consistent FPS), but I'm continuing to have problems with most of my mid-caps (mix of King Arms and MAG brand).

Is it possible that it's an issue related to the spring tension inside the mag. Are the mid-cap springs too weak to move BBs up into the hop up chamber? Is this perhaps a problem with the hop-up unit? Have the offending mid-caps reached the end of their life?

I was playing today and noticed a similar problem with my mid-caps on my VFC scar. With the VFC the problem is not as severe; it miss-fires every 5th BB or so. The same mag in the King Arms will fire the first shot, but none after that.

Spring tension deficiencies are usually more prone in high-caps rather than mid-caps. I've yet to have feeding problems with midcaps on either m4 or g36 series magazines.

Since it's happening with every KA magazine I doubt it's the magazines since it's highly improbable that they all reached a point of failure, but if you've done some nasty stuff with your mags I wouldn't be surprised.

This could be a side issue: what brand of bb's are you using? I've heard feeding issues with systema magazines and certain brands.

The hop-op could be an issue. Depending on if the plastic that forms the hole that makes contact with the magazine pushes the stopper sufficiently. You said you added a velcro to the back which should have stabilized and fixed that issue.

Make sure that the hopup chamber makes sufficient contact with the stopper. Due to the tolerances of my jg g36 had feeding issues with cyma magazines that were alleviated when I filed off some of the shell. They're still hard to insert (hop up chamber and bb hole don't fit 100%), I have to push them in hard, but they still feed flawlessly. That could be the case for your KA M4 but it's kinda stupid how the magazines made from the same company as your gun might not be compatible.

BB Bastard 0.28 Bios is what I'm using

The KA hop up unit is metal and the only thing I've done is changed for a flat hop. When I look down the barrel its not like there is anything protruding that might stop the BBs from being fired, plus changing the hop up rubber is a relatively simple process

I mean Id hate to be at a game, borrow a friends mag only to find it doesn't work because of some tolerance issue in my gun.

I'll check how the mags are sitting in the hop unit

Some brands of bio bb's actually do have feeding issues, and I do believe BB bastards is one of those brands. Hopefully someone else can chime in on this revelation.

http://www.airsoftcanada.com/showthread.php?t=167135

Hmmm. I'll try my non bios this weekend see what happens.
This sucks because I just got the case of 10K 0.28s

I just completed a bunch of testing using various ammo and magazine combinations. The only other type of ammo I had access to was Valken 0.25s non-bio. The BB Bastard Frag ammo seems to be problematic from what I can tell, and my King Arms mid caps seem to be the worst performers. I'm kind of upset because the sales rep (at Hero's) who sold them to me implied they were the same as the regular BB Bastard ammo, which they clearly are not. I definitely won't be buying Bastards any more, there wasn't a scenario I could come up with where there wasn't at least a minor problem)

Also, my MAG brand magazines don't seem to sit well in my magwell. After about 5 shots the magazine's spring trys to push more BB's into the hop-up, but instead pushes itself down and out of the magwell about 1/4" which prevents and more BB's from feeding.

Here is a chart I made that summarizes my findings. Red is the worst, with no feeding possible in all but the most forced scenarios. Green is no problems, or what I would consider perfect, light-green is "usable" but with minor problems. Yellow is frustrating and inconsistent feeding.

Some magazines have #s which correspond to a labelling system I have on these mags to keep track of which ones I'm using in-game.

http://i.imgur.com/5mRYXWp.png

Looks like the bb's were a contributor but not the causal factor. I would still try to modify the mags to sit better in the magwell/receiver. Duct tape usually works, just to keep it in place and prevent wobble.

There were definitely multiple factors at play; before I fixed my nozzle I was getting mis-feeds and double feeding in all of the "green" scenarios above.

Now I've narrowed it down to a game of mag type + ammo type.

The mags are pretty sturdy (almost no wobble) with the velcro mod, and it's only the MAG brand mags that are "un-seating" themselves. I suspect this is a problem with the mag release and the location of the notch in the side of the MAG mags where they are held in place.

Edit: This thread has taken a turn since the problem isn't my gun any more.
I might post my chart as a separate thread, or post in another thread dealing with ammo/mag problems.