Okay guys and gals, I’ve upgraded my M4. Of course, you know the saying “The best laid plans…” well that seems to be the case. After putting it all together with the new Madbull Spring, the Madbull Piston, Element Silent Piston & Cylinder Heads, and Element Spring guide, I was excited to test it all out… then came the disappointment.
I fired the gun on semi-auto. Nothing but a slight whine of the motor. I made sure the battery (a 9.6 mini), was fully charged and tried again on full auto (thinking that the gearbox might be bound up). The motor made a solid “zip” sound and that was it. No bbs flying at 400 fps for me.
Disappointed, but determined I tore the gun down again. I quickly figured out the problem as I looked at the spring. It was currently compressed fully (coil on coil), but unable to compress enough to allow the sector gear to release the piston! The culprit was the combination of the bearing spring guide, the bearing piston head, and the m120 spring! The spring was longer than the stock spring, but due to the decreased room created by the bearings at either end, the spring just didn’t have enough room to compress and release the sector gear. So in the end I did without the bearing spring guide. Sad I must say, but necessary. The stock spring guide is a metal Classic Army spring guide, so I’m not worried about durability, I was just trying to improve the efficiency of the gearbox.
Okay, now I’m sure you’re thinking… where’s the teardown and rebuild pictures? Where’s the review of the internals? Well, all in due time young grasshopper. I want to get the gun chrono’d first. Also, I did have the fortitude to take a rate of fire measurement before doing the upgrades, and will do one after as well for comparison. So look for that as part of the M4 upgrade reviews.