Erratic piston behavior
 

This is my first post in this forum. If this is an already answered question, please don’t trash me too hard and direct to there! I have a JG M4 and use it for IPSC competitions. One of these days, suddenly its piston started to lock somewhere towards the back, but not at the rearmost position. Sometimes I just have to switch to full auto to have the piston released, other times even this doesn’t work. After fully recharging the battery, I removed the upper and placed the switch back to single, and, while pressing the trigger, forced the piston all the way to back. This maneuvers (gosh! I hope I haven’t damaged anything beyond repair!) released momentarily the piston and the gun fired properly in full auto, but when switched back to single, it locked again!!!
What is going on? I humbly beg for guidance!
Ed, from Brazil

What strength of spring are you using, and what size and voltage of battery are you using?

The spring is the original one. Never replaced. I don't know more about it and the battery is also original (hit me, if I deserve!) 9.6V. This gun went through a full IPSC tournament without a glitch (only single shots allowed, fired very quickly), but since then, it is behaving as I've said... Suggestions?

It maybe possible that it is the battery that is causing the jams.
The last time I worked with a JG gun that came with its own battery I found that the battery was extremely low quality and after a while stopped holding a charge and even though at first it did provide enough power to turn the motor to compress the spring after a while I found it could not even turn the motor over. A new battery fixed that issue for me.

Buy a new battery, The stock JG one suck ass and die fast, your problem is most likely just your battery being too weak. (and fully charging is no help when a battery is in this state)

Thanks, ya'll!!! I'll try new batts and report back!

I also vote battery.
I highly recommend cheapbatterypacks.com. You can make a custom pack for very cheap and out of high quality cells (elite). Very fast service and the quality is extremely good.
Hope this helps.
-Brett

I've seen the piston locking back thing in semi, and needing full auto to unjam it......... often times it's from only pulling the trigger halfway then releasing. Try cycling the gun in semi by pulling full strokes on the trigger and see if the problem still happens.

BINGO!!!
 

Thank you all!!! It was the batteries! As soon as I've connected a set of Kings Arms 11.1 V 1100mAh batts, the thing just flew!!! The remaining question is why haven't I replaced the batts before? Because I'm a newbie! Hahahahahahahahaa! Do you bestow "duh" awards in this forum?
Again, thanks to all who took their time to help!

Ed

No problem haha. So did you buy the King Arms battery? If you did, be careful in full auto with that strong of a battery. That is too much juice for a stock JG, and you eventually end up stripping your piston. I have a friend who has a JG 614, and even with a 8.4v battery (the stock battery), his piston is taking wear.