Piston Jamming

[Jaren Fearsore]

Weapon: M4 Assault Rifle (Make unknown, I picked it up from Esteban last year, and he told me what the model was, but it seems to have slipped my mind)

Problem: Piston will seemingly jam after 40 or so rounds

Additional Info: As stated above, after firing some rounds, the gun will stop firing and will make a slight click noise when I pull the trigger. Upon opening it up, I find the piston stuck. Pushing upon on it with something and at the same time pulling the trigger, the piston will snap forward and the gun will resume firing. This has happened twice now.

Any advice on why exactly the gun is doing this, and what replacement parts I might need to pick up?

[Esteban]

Hey man. I had that problem for as long as I had that rifle. I found that using a higher power battery solves the problem. The gearbox came with a short, stiff spring that is difficult for the motor and 8.4v mini battery to pull back. Try using a mini 9.6v or any other higher power battery and shoot through a hi-cap and see if you have the problem. You may have to get a new motor for it. This was the reason I sold it to you pretty cheap 

[Jaren Fearsore]

Alrighty, I'll give the battery a try. I'd prefer not to have to replace the motor, but eh, we'll see.

[Esteban]

The stock 8.4v mini is strong enough to pull the spring back and fire for the first few shots, but it'll drop its voltage and your gun won't cycle after that.

[Pyrus_Conflagarus]

a couple other tips:
-Check the shimming.  if you have too much friction in the gears, it will eat your battery.
-downgrade the spring- the less energy required to pull the spring, the happier your battery will be
-either get a higher voltage or higher mAh battery. A 9.6v is all well and good, but something that will o/p a higher level of current for longer will accomplish the same thing.  For instance, I tried an 8.4v 1100mAh battery in my FAL, and it hardly compares to the 8.4v 4200mAh battery I use in it.
-Lube it up.  everything is better with enough lube

I can recommend a few other mods, but those get a little pricey.

[Dominum]

Both good advice, your question should be thoroughly answered .

Along Pyrus's line of reasoning, I have to ask when the last time it was tuned up was?

[adjunog]

First, To check the motor if it's working-pull out motor and connect, hold firm around the can and not polars, pull trigger.
Second, To check gears/internals-M.box still close, move bevel with a tool, if it moves freely it's not the gears but that it still can't be the case.
Third, Internals-check for debris, metal chunks, or foreign objects.  It's best if you clean the whole box b/c all soiled material will collect in a clothe of a sort to easily determine your clogs or jams.  Also it'll be easier to inspect your gears, piston channel, piston, etc. for chips and gouges.

If you haven't determine your faults please post to let us know your progress.

[Dominum]

By "moves freely", I assume you mean moves freely right to left after the anti reversal latch has been completely tripped?

In any case, there's really no need to open it, if it fires fine for a half a mag and then can't manage it then it's either the battery or the motor (may be mounted too high as well), not a mechanical failure.