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Ian_Gere

BB feeding problems

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The problem: Sabine (my AK, see below) has developed a BB feeding problem issue. I can't remember when it began exactly, so I don't know what I'd just changed. I'm pretty sure it began as something very intermittent and got worse, but it didn't get gradually worse, but that's no surprise because I started fiddling around swapping parts out trying to find a combination that would sort it out!

 

Needless to say, I couldn't, and now it's 'kin unbearable! I tried a Mad Bull Shark rubber as a solution, but I couldn't get it to fit into the hop unit properly and then it got jammed. I wrecked it getting it back out :( doh! Still, I had 3 different other hop rubbers and none of them helped.

 

I haven't tried a new tappet plate, but I have no concerns about the one I have - it's not warped, cracked or damaged at all. I've tried a few different air nozzles too. 1 definitely makes it worse, a PSEM one that is slightly longer than the stock one. Annoyingly, even though I have an upgrade one that appears to be exactly the same shape as the stock one, the stock one does seem to make the problem ever so slightly better, but it has cracks in it and no O-rings.

 

Sometime in my attempts to find a solution, the feed tube of the hop unit got bent a fraction - I wouldn't have believed this was possible without busting it completely but a gun-tech at Ground Zero told me it does happen to plastic hop units sometimes because it can get clattered by inserting mags in a hurry. So I bought a nice new Lonex metal hop and, just for good measure, a Lonex 50 deg. rubber and a pretty little violet anodised aluminium nozzle with a fitted internal O-ring...

 

You've guessed it: it still doesn't effing work! AAAAAAAAAAAAAAAAAAAAAAAAAaaaaaaaaaaaaaaaaaaaaaaaaaaarrrrrrrrrrrrrrrgh!

 

I have got a set of Prometheus gears in her, and I thought that maybe because the pin on the selector gear is of smaller diameter than the stock one, it might not be operating the tappet plate properly, but I've measured it and compared it to the stock one: the outer edges of both pins are exactly the same distance from the centre axles of the gears. Besides, although the original stock one is missing 2 teeth, I have another one of the same type and it doesn't help.

 

I have ordered one of those sector chips to delay the tappet plate (I was advised by Fire Support to get the King Arms one because it's made of POM so easy enough to modify if it doesn't quite fit, which sounded like a good idea so I did). Has anyone any experience of these things, of any make? I do think that the increase in ROF due to an ICS Turbo 3000 probably contributes to the problem, but I do remember for definite that the problem didn't begin as soon as I put that motor in, because when I did it I considered getting a sector chip then, but as there was no problem, I didn't bother. I have had 2 different new pistons in though and a different piston head, along with some variations of piston head O-rings and Kanzen bearings too and some combinations definitely run faster than others.

 

Anyway, is there anything you can think of that might be the problem? Any advice on solving a similar problem? I'm at a stage where I'll 'kin dance round a maypole in my scuddies chanting Baa Baa Black Sheep with it if someone can come up with a plausible explanation as to why that might help!

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The only thing I can think of, from what you have described you have looked at just about everything.

 

However, have you looked into the hop chamber, and fired the gun? Does the airnozzle cycle in it properly, i.e. actually pulling back further enough to allow a bb to feed?

 

I have seen a similar issue to yours, no explicable reason for it not to work.

The issue was the tappet plate was not being pulled back for long enough. Simple solution: install a delayer on the sector gear, this means the tappet plate is pulled back for longer, especially useful in Hi-ROF projects.

 

Otherwise, I can't really think of anything else without seeing it myself. Have you tried other mag brands? Maybe moving the mag in the magwell at all... some need pushing forwards!

 

Best of luck.

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I've got 5 mags of 4 different types and none of them make any difference. I can't think how to see if the air nozzle is pulling back far enough with it in place, unless I had a clear hop unit, which I don't, but when I fire the gearbox outside the gun, the nozzle moves back and forth definitely. TBH though, it's so fast that I'm not sure I could tell if it's going back far enough. Unless the tappet plate is jumping off the pin on the sector gear, I can't see how it could not be going back far enough, well, without being too long for an AK anyway. Does anyone know if the tappet plate can spring forward early by jumping off the side of the sector gear? I don't know if there's enough space in the gearbox for that to happen.

 

Yeah, I'm desperately hoping that the sector chip I ordered does do it cos that's all I can think of too. It's just that I'm really dispirited with it now so I'm prepared to accept that I'm a numpty thus could easily have missed something and somebody else might spot it.

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It might be that the motor is cycling the nozzle back and forth faster than the magazine can feed the BBs, I assume you're using hicaps, right?

 

Try winding them to their absolute limit to get the most tension you possibly can onto the BB and make sure they're packed to the brim so they definitely pick up enough to fill the feed tube. If on the 22nd anyone has any AK midcaps, I'd advise giving them a go, you never know what difference it might make.

 

I've found that all my guns have always fed better on mids than highs because they're under direct spring tension instead of a clockwork type mechanism.

 

Short of that, did you replace the motor because the last one burned out, or just as a general upgrade? It might be worth putting the old one back in if you can, just to test that specific diagnostic. If a weaker motor solves your problem then the sector gear delay chip ought to definitly solve your problem and you'll be alright to go back to the ICS motor once the delay piece arrives.

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It might be that the motor is cycling the nozzle back and forth faster than the magazine can feed the BBs, I assume you're using hicaps, right?

 

Try winding them to their absolute limit to get the most tension you possibly can onto the BB and make sure they're packed to the brim so they definitely pick up enough to fill the feed tube. If on the 22nd anyone has any AK midcaps, I'd advise giving them a go, you never know what difference it might make.

 

I've found that all my guns have always fed better on mids than highs because they're under direct spring tension instead of a clockwork type mechanism.

 

Short of that, did you replace the motor because the last one burned out, or just as a general upgrade? It might be worth putting the old one back in if you can, just to test that specific diagnostic. If a weaker motor solves your problem then the sector gear delay chip ought to definitly solve your problem and you'll be alright to go back to the ICS motor once the delay piece arrives.

Yeah, hi-caps. Funnily enough I was going to buy some mid-caps but I ran out of money this month (well, ran out of overdraft and I owe my g/f £50 as well :() but the reason was eliminating rattle and cos I'm getting a bit better at mag changes under pressure (although I did see a utube with a British Soldier in a firefight with Taliban nutters taking yonks to change mags, like, longer than me ffs!). I'll see if anyone has any as you suggest.

 

No my other motor didn't burn out, I just wanted faster trigger response, and I got the Turbo 3000 for a tenner on eBay! I've resisted taking it out again because of the bloody soldering. The sector chip should arrive either 2moz or Monday am though so I'll try that 1st. But beyond that yeah, that'll have to be the next, backward, step grrrrrrrrrrrrr!

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Alternatively, you could put your mag in, turn the gun upside down, remove the mag and using your thumb, hold the BBs in your hop unit from falling out. This should provide enough tension to fire a single BB.

 

If that works, then it is a simple case of lack of tension, and/or too much ROF!

 

Then again, I've had an ICS L86 LSW firing at 40rps, fed beautifully on hi-caps!

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Good plan GP. Results: I held the gun upside down and dropped the BB's into the feed tube and then pressed on the top one which stuck out a little - shot 1 no BB fired, shot 2 BB fired, shot 3 no BB fired, shot 4 BB fired, shot 5 BB fired, shot 6 no BB fired, shot 7 no BB fired, shot 8 last BB fired.

 

I don't think it's a tension issue - when I'm using them I keep my mags wound right up to the limit, just in case I get caught in a position where I need to properly hose the enemy and don't have time to wind on while I'm doing it - the habit has stuck. With the gun upside down there ought to have been nothing stopping the BB's just dropping in and being fired even with the first shot, although it never fires the first shot using a mag. It's got to be the speed the nozzle moves at or that the tappet plate is jumping off the sector gear pin... surely to fμ<Ж!

 

What do you think?

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In regards to the delayer to put on the sector gear, Arden has one in his M16. I fitted it really easily, literally took the gearbox out, took on half off and then just pushed the delayer chip on the sector gear while someone held the tappet plate out the way. His gun was misfeeding every other shot on auto, and now it feeds fine.

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Well that's encouraging, Liam! Thanks.

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Well, the sector chip does seem to have made the movement of the air nozzle more obviously correct, but the gun still isn't working. I think it's a seal problem between nozzle and hop rubber now, but also the barrel base assembly is slightly twisted and the hole into which one of the hop unit screws fits is stripped so the screw is loose. That adds up to the BB feed tube being at an angle a bit. I've managed to bodge a partial fix, but I've yet to suss the seal problem.

 

Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaarrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

rrrrrrrrrrrrrrrrrrrrgh!

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If you're bringing Sabine tomorrow, I'll have a look with you at lunch, I fixed a mate's AK earlier so AK knowledge is all fresh in my mind, a fresh pair of eyes might be able to notice something you've overlooked. You never know.

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If you're bringing Sabine tomorrow, I'll have a look with you at lunch, I fixed a mate's AK earlier so AK knowledge is all fresh in my mind, a fresh pair of eyes might be able to notice something you've overlooked. You never know.

Yeah, and if I'd noticed this post before, I might have done just that! Doh!

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Don't know if my CA MP5K PDW's got the same problem. I'm really dissapointed with it because it's been having loads of problems since I first got it.

The first was when it would run out of charge really quickly, about 30 mins, then it would stop firing and I'd just hear a clunking noise + feel something moving in the pistol grip so I thought it was the motor.

Somebody suggested it could be overshimed and forcing the motor to work too hard or something. Turns out it's just the bad battery that came with it (and that's why more expensive guns don't come with them, I discovered)

Still though, it doesn't feed very well.

I've tried tapping it and lubing it like the instruction booklet suggested but still the included 200 round hi-capacity magazine doesn't feed as it should be doing. The CYMA 65rnd short magazine I've got also has problems but it's because it's not perfectly compatible and has to be pushed in more, but it's annoying.

Just wondering if you might know what to do and if there are any other good magazines to use with it.

Thanks :)

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I'm afraid not, mate. The clunking in the pistol grip but not firing sounds familiar though. I had that when the mosfet i put in failed. I'm guessing that not enough current was flowing to spin the motor, but some so it pushed against the spring a little. A duff battery could do that. My 1200mAh battery that came with my CYMA AK is crap, but it's not actually so bad it doesn't work, it just runs out in about 40-45mins of hard use...

 

Have a good look at the feed tube (the bit of the hop unit that pokes down to the mag for BB's to go up) and see if it is perpendicular to the magwell. Mine wasn't which is why I got a new hop unit. Still not sorted though grrrrrrrrrrrrrrrrrrr... Still, I haven't had time to try swapping hop rubbers and air nozzles around to see if some combo will work yet.

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