"Just installed and used this spring yesterday. I got the M100, and was hoping that it would boost my FPS to the 360-370 range, based on the range listed. Unfortunately, my gun only chrono'd at around 320-325, so it was already at the low end of the advertised range. Disappointing, really. Guess I'll have to try something stronger, and hope it doesn't push me over 400.
"Given the good ratings this has gotten, I had high expectations.
I have a CYMA CM042-S AK47S.
I bought a Matrix 3000 Magnum High Torque motor to use with this, which, given its reviews, should have been more than enough. I got everything set up, but the motor couldn't pull it back all the way, and the gears just locked, and the fuse blew. Eventually, after MUCH messing around, buying of different parts, etc., I decided to do some testing, and realized that this spring, when compressed fully, is still too long to allow the gun to fire. aka, the distance the spring is completely compressed, so the coils are smashed up against each other, it would have needed to have been compressed further than that to release, which is not possible.
All told, this problem caused:
* Two full sets of destroyed gears: the stock set, and a new Matrix High Torque set, along with the stock pinion gear
* Broken stock piston
* Warped gearbox
* Innumerable wasted shim jobs
* About 5 blown fuses
I'm very disappointed, as I thought that this spring would fit virtually any AEG, especially something as mainstream as a CYMA AK47. However, it is too long and has too long of a solid compression length, rendering it useless.
"Good spring, works great and if you have a quick-spring-change gearbox, it becomes no problem to install because you dont need to open the gearbox. But if you have a standard gearbox without a quick-spring-change then look up some videos to show you the right technique to install it without too much trouble. Hint for those with normal gearboxes, use a screwdriver it guide/push the spring and spring guide back into place.