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ICS Complete Upper M4 / M16 GearBox with full reinforced internal Airsoft parts
by Jason A. Date Added: June 13, 2010
I have only 2 gripes about this kit: The ICS aluminum piston is a gear shredder. Toss it, or sell it to someone building a semi-only DMR. Second, WHY would you put a bore-up cylinder on this that is ported?? If you plan on using this with a barrel longer than 420mm(probably more like 380....those are some big holes) buy a FULL CAPACITY BORE-UP cylinder.

Note, you will need to have high torque gears. it doesn't advertise the FPS on this kit, but with .25s it was shooting 420 out of a stock 363mm barrel. The main thing that prompted me to swap out the piston was that it was completely stripped.

I replaced the piston with a G&G Reinforced, and swapped out the cylinder for a Systema full capacity bore-up, and dropped in a 110 spring to allow it to comply with local FPS rules(and even then it had to break in a little before it was under 400), and its not running great.

EXCELLENT compression. Even with a 110 this thing was pushing 410 fps(broke in to just under 400)
Except for the piston, quality parts
Bore-up piston head and cylinder head, ideal for longer barrel set-ups

Piston is garbage for full auto users
Spring included puts it over most full auto FPS rules, and under standard DMR performance.
Cylinder included is probably not the best choice, as bore-ups are more for longer barrels.

Rating: 4 of 5 Stars! [4 of 5 Stars!]
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