Cyma Thompson Problem
 

The problem I am having is this. On semi the gun will load and fire 1 round and then just dry fire. If I remove the mag and reencert it the gun still fires just 1 round and then dry fires. When I switch the selector to auto the gun fires full auto with no problem. If I switch the selector back to semi I get 1 round and then dry fire. I have 5 mid caps which I do not know what make they are as they came with the gun. The fact that it works fine in full auto but not in semi has me baffled. I have looked at the mag well with the mag out and in semi I can see the nozzle working like it should when I fire the gun. I am kind of thinking mag problem but again it works fine in auto. Any suggestions would be helpful. I guess I should add when I remove the mag after the gun has dry fired there is always two BB's roll out, which indicates the mag is feeding

What kind of bb's are you using?

I had a the same problem in my AK, and all i had to do was put in a gear sector clip in the gearbox. Problem was solved.

I use MadBull .25's. so it shouldn't be the BB's. Now I do have some 20's I guess I could try thoses, I think they are Bastards so again good quality ammo. I look around and see if I can locate a sector gear for replacement but I'll wait and see what other ideas pop up first. If it was the selector switch it wouldn't fire at all in semi, is that correct. Thanks so far guys.

What battery are you using? Does it happen with the hicap as well?

No hicap, just 5, 130 round mid's. I am going to have to guess at the battery as i'm at work and can't check. I believe it is 9.5 1100mah, with small Tamaya connectors and it is fully charged (made sure of that). I haven't had a chance to get the Deans connectors done yet, I do have other batteries but they all have Deans so I can't try another battery yet. I'll add that when in auto it has great range but I don't know the FPS, that I can check this weekend as my buddy has a crony.

Wouldn't be the battery. The gun either cycles or it doesn't.

No problem with the gun cycling. I pull the trigger the mech cycles, just in semi it will fire 1 round and then dry fire (cycles) but will not fire BB's. Yet it is fine in auto (cycles and fires BB's.

Hi, just spoke with our gun tech, and he says that none of the above would cause the problem. He wandered if you bought the gun second hand, as the CYMA comes with one mag in the box, and not 5. If the gun has 5 mid caps it's likely that they could be King Arm's mag's (as they come in packs of 5), and they're not known for their quality. He suggests that you try some silicone in the mags, and then load and unload them a few times. If this doesn't work you can PM me and I'll put you in contact with Frenchie.

I will give that a shot and yes it is a second hand gun. Now that you meationed that I remeber I had to something like that with my AK mags. It is worth a shot. If not I'll get bake to you. Thanks to everyone who replied, it is great having a way of wiring into some many people when you need help. Cheers.

Is this a new gun for you? If not just wondering does the original mag work ok? I have this gun for about 3 years and never had this issue.
Tis strange.

Good luck

Tank

Also, you could try firing it upside down. Another permanent fix, if it's the right problem, would be to shave down the BB retainers in the mags (the wedge shaped pieces that hold the BB's in.)

had a similar problem with mine after i switched out some of the stock internals. pull out your mag, look into the receiver and see if the nozzle is sticking out or not, cycle it once and see where it ends up. that was my problem, in auto it would jerk back just enough to feed, but in semi it didn't. i ghettoed it by just taking a file and shaving a bit off the end of the nozzle. haven't had a problem, and get a consistent 368-372 on .20

Check your tappet plate also, It's way too damn flimsy in that gun.

^^

+1

try this but dont remove any more than half a millimetre. the sector chip will also work.

If it's the stock nozzle, I would certainly not touch it. The problem is elsewhere. Could throw off your seal with the bucking.

I just got in, I'll play around with it this weekend and post back later if I figure anything out. Thanks again guys.

This was actually my gun originally. (didn't know it was having this issue when I sold it)... They are king arm mags, and yes, silicone in the mag and filling thematic few times is a very good idea. Couldn't find the hicap to go with it, so he doesn't have it. That's about all I can add help-wise... Never had any other issues with it, nothing should be broken in it, but I suppose it's possible...

Also everything internal is stock on it.

Thanks for the added info. I actually got a chance to look at it tonight after all. I tried the silicone in the mags but it didn't really do much. I not sure about the filing of the nozzle at least not yet. What I did find is the nozzle seems to stick out just a hair more when fired on semi then on auto. I compared it with the distance the nozzle sticks out on my AK and it is about the same in auto but more in semi. I am wondering if the tappet plate is worn in some way. I saw some for V6 mech and they are not that much so I will probibly order one and it can't hurt to replace it . Holding the gun upside down did nothing as far as improving feed but you never know till you try.

Just a bit of a follow up as I've had some time to play around with the Thompson. I did the silcone as meantioned last night and as of last night it made no diffrence. But I got home to night and popped the same mag in and I guess the airsoft gods decided to be kind because she worked in semi. I put in an unsilconed mag and it still worked but not as good. Now something else I did was misted a little silcone in the feed throat of the hopup so maybe that did something. Anyway it works, so thanks again folks.