Confused with my M4
 

I bought an AIM M4 off my buddy after he has problems with it. In stock form the motor and battery heated up before the battery died after a few shots. Believing it might have been something wrong with the motor, I replaced it with a Classic Army. To my dismay this didn't clear the problem. After doin plenty of research on which route to go I bought every part to completely replace everything inside. I chose to go with an Airsoft Surgeon Stage 3 spring with Guarder torque up gears. According to all the spring charts the spring is rated around 463fps. When it was chrono'd at the shop is only shot like 386fps. I'm using a 10.8v battery so it has plenty of power. The only thing I hadn't upgraded was the barrel but this shouldn't have that much impact would it ?

I don't have much experience with AEG internals but have you tried using a new battery? Not trying to repeat whats been said many times but Ni-Cd batteries suffer from a 'memory effect' when not properly discharged. The memory effect lowers the maximum capacity of the battery and can lower it to the point your battery won't be able to hold much of a charge.
-VM

(This should be in the Doctor's Corner I believe)

Yeah I bought the battery when I bought all my upgrade parts. It's a G&P 10.8v 2200 mAh NiMh. If i read right, you're not supposed to discharge NiMh batteries.

Sounds like an airseal problem. Check to make sure the hopup isn't torn - you may want to wrap it in some teflon tape (google will show you how to do that). Also, check the piston and cylinder head o-rings - they may have shrunk or torn. Also, if you have a cylinder with a hole in it, make sure the whole is at the back (towards the stock) and not the front (towards the handguard).

Ultimately, you cause yourself more headaches when mixing-n-matching parts - each manufacturer has different tolerances and QC, so in my experience I've found you get better results when sticking to parts all from the same manufacturer - at least in the major systems (gears + piston, piston head + cylinder + cylinder head).

A complete list of parts in your gun would help diagnose the problem - otherwise, send it to a gun doc.

hey screw, is this treflon mod applicable to ar's? i could only find info on m324 or spring gas guns. do you got a link?

Use the same method as the bolt-guns - just one wrap around where the hopup rubber ends, and slip the little metal "ring" that stabilizes the hopup rubber over the tape. It ensures 100% airseal between hopup unit + barrel, but M4 have other air leaks, esp. if you use a 2-piece (TM-style) hopup.

Here's the list of all my parts:
Guarder Reinforced Gearbox, Guarder Torque Gears, Systema Piston, Hurricane upgrade kit, Systema tappet plate, Airsoft Surgeon Stage 3 spring, and Classic Army Torque motor. My buddy bought the hurricane kit and new set of gears for his AK and it has more FPS than mine. Something just don't seem right here

Well I have found one problem with my gearbox...it's cracked. What would someone reccommend for a new gearbox? Apparantly this Guarder one didn't cut it.

Pro-Win gearbox... ;)

Can't seem to find anyone that has them in stock. Also is the regular hurricane cylinder kit a bore up one or just an upgraded stock one ? If so that might be why i'm not getting the best out of my spring.

I have a Pro-Win 7mm in stock.

The Hurricane cylinder kits are a standard bore.

I second the air seal issues. Best way to check is to have your gun unassembled - hold the muzzle of the inner barrel against the air seal nozzle (don't use the other end because the hop up packing's hole presents an area for air seal loss) and with one BB chambered, firing it through a chrony. This method should provide you with the maximum possible velocity with your setup with maximum efficiency and minimal air loss. (Keep in mind that the air seal nozzle will jack forward before it shoots. Keep this in mind so that you don't press the inner barrel against the nozzle too tight.) If you have a huge variance between that velocity with your assembled velocity, then chances are, you are losing air somewhere in the hop up unit. The M4/M16 serious is notorious for having one of the poorest air seals in the hop up chamber. It's even worse if you have a plastic two-piece chamber.

I just built a gun that had a 80fps variance between a good hop up chamber and a poor hop up chamber.

As it stands i'm gonna try another Guarder gearbox, cylinder kit, and metal hop up unit and see if this changes anything. I don't want to drop too much money into this and save it for my psg-1.

pm bug, he has an unassembled pro win hed prolly be willing to sell.