I only buy ICS or G&P M4s these days. Of the 40 airsoft guns I've purchased in the last three years, six have been from ICS. ICS builds solid feeling, solid performing, reliable AEGs.
The highlight of ICS's M4 offerings is the split gearbox. You can:
1. Buy separate upper gearboxes to change FPS on the fly, or swap to a fresh upper if your piston strips. One pin, that's it.
2. Very easily change out compression parts (spring guide, spring, piston, piston head, cylinder, cylinder head, nozzle, tappet plate).
3. Build a DMR without trying to close a whole gearbox with an M150+ spring.
4. Shim the pinion to the bevel gear visually. The upper half of the gearbox isn't blocking your view.
If you can't tell, I like ICS as an upgrade platform. They perform solidly out of the box, but are exceptionally easy to upgrade. If you are new to gearbox work, ICS M4s are a great place to start.
Note that ICS M4s use imperial threads; this means that you will want to stick with G&P or ICS front ends to avoid modification. If you want to get all Magpul with it, you will want a G&P delta ring.
- Split gearbox.
- Solid construction.
- Nice stock. I'm 5'8", and the length of pull is comfortable. Also, ample battery space.
- Nice enough handguards. I prefer rails, but these are functional.
- Spring tension release via forward assist knob.
- Good stock motor.
- Good stock accuracy. Some don't care for the ICS hopup chamber, but I love it.
- Superb lower gearbox components. Every gun I've gotten has been well shimmed.
- Good wiring.
- Several nonstandard/non-Marui parts, including:
Front sight (Allen key mount instead of pins)
Stock prongs are too thick to accept standard stocks without modification
Stock post design can't easily be trimmed to accept short G&P style stocks
I've had a hard time getting certain other parts to play nice, including: air nozzle, trigger mech, and tappet plate
- While solid, receivers are nowhere near as pretty as G&P.
- No functioning bolt-catch.
- Middling quality upper gearbox components.
- Mushy fire selector (only this one of the 5 ICS M4s I've picked up had this issue, so I'm thinking dud, not feature).
Do I still recommend this gun, despite the long list of cons? Yes. Over and over. The spit gearbox is brilliant. Most of the nonstandard parts exist to accommodate the split gearbox, and ICS's quality is great. I've never had a metal receiver of theirs break. The guns are reliable without upgrades, and are very easy to upgrade if you are so inclined.