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For: JBU M120 Upgrade Kit for M4 AEGProduct Information:
The JBU Tune up kit for m4 is a great way to gather the parts I needed for the start of a major upgrade. The aluminum nozzle, aluminum piston, aluminum piston head, aluminum cylinder head and chrome plated cylinder create superior compression compared to the stock plastic CA m15a4 cylinder internals. I just put my finger over the nozzle and slid the piston in and out to check. Changing these parts and the stock spring guide for a better one with ball bearings (included) prepared my aeg for stiffer springs. My CA m15a4 carbine has metal gears and metal bearings already. I added a Guarder SP100 spring (my field limit is 400FPS) and a 363mm Madbull Ver 2 tightbore barrel (6.03mm) to make my CA m15a4 carbine complete. It can now pierce an aluminum can through the center bottom (approx 385+ FPS). Be sure to have the cylinder grease, silicone lube, shims, tools, and patience to put it all back together if you plan on doing this yourself. A 9.6V battery pack is necessary to complete this project. My 8.4V pack just did not cut it. I highly recommend the video from mechbox.com on upgrading the spring for a version 2 gearbox as a guide for disassembly and reassembly of the gearbox. http://www.mechbox.com/mechbox/v2-mechbox-spring-upgrade.htm-
As the other reviewers have noted, the metal cylinder head, piston, and piston head make your gun louder with a crisp recoil sound.
These are very impressive, high quality metal parts for the price. I am breaking them in now and time will tell how well they perform in the long run.
High Quality Parts
Nice Combo if you don't need gears or bushings
Great Upgrade for CA m15a4 series, the piston fits the rails
Fun project for airsoft-smiths and gearheads
Nice recoil sound (maybe a con if you want a silent head)
This kit would be better if it came with the cylinder lube.
There is no instruction sheet at all. I had to research all the info online.
This is not for someone that is unfamiliar with how the version 2 gearbox works.
Just don't plan on using a 8.4 V battery pack with this kit and stock gears/motor.