The M4 S-System is essentially an M4 with rails all over it. Maybe eventually I'll put a red dot, grenade launcher, laser, and flashlight on it. The possibilities are pretty much endless. This gun is also mad fun to shoot, especially with a freshly charged battery. The average RPM is about 850 and the FPS is around 400-406. The whole thing is metal except for the grip and stock, which I believe aren't metal to begin with. The stock has 6 adjustable positions for longer range encounters and CQB. Mine has a foregrip/bipod on the front which only cost 8 dollars but makes a large difference.

Pros

- Insane stock FPS
- Plenty of rails allow for maximum customization
- 6 Adjustable stock positions
- Good hop-up system
- Mostly metal
- Ver. 3 updated gearbox
- Operation isn't complicated at all
- Cost only $129, and I got mine on eBay brand new

Cons

- Pretty heavy
- Not exactly sure how long it will last, but it did its job and got me into AEG's.

Overall-9.0/10
Only because it isnt a Classic Army, TM, ICS, etc.