Ok, well as it a M4 there pretty much nothing you can't upgrade! but to get more power and range out of a AEG there are what 5 main things to upgrade, heres a list:
1. Spring, get a good spring will give you more FPS I'd say a M100 for around 350FPS.
2. Hop rubber, this will give you the extra range by about 15yd or so. (Systema Hop rubber are the best from what I've been told)
3. Inner barrel, now as its a AEG I would get a 6.03 tight bore barrel, this will give you a small amount of FPS increase, little extra range but will give you much tighter grouping at range. (Prometheus would be your best bet here, but also you need to take into account the length of your inner barrel, if you can't fit a barrel in your need to go smaller this will mean you lose range, but with the upgrade hop rubber you wouldn't really notice it)
The rest is optional.
4. Piston and piston head, this will help to give you a tighter compression = more FPS and can also effect your fire rate.
5. Gears, this mainly helps with a smooth action of the shooting and help with high fire rate gun, Lipo etc.
6. Bearing, I have 8mm standard cheap rifles have 6mm ball bearing, I recommend 7 or 8mm.
7. Motor, this is mainly to do with fire rate, or torque, but as we aren't in the USA we don't need to balance our motor with the spring strength. So for us in the UK this is mainly to do with fire rate / control. (recommended G&P M120)
8. Hop chamber, this helps with feeding, rate of fire and a wee bit of range.
Thats not everything, you can do but that the most common things you can do, and to help you get more range and power out of your AEG.
Hope this helps, PM if you have any more questions.
Tristan
