Thanks go out to xsboredom on Airsoft forum for presenting the idea - http://www.airsoftfo...op-t124264.html - and answering all my PM's about it, Allizard for creating this thread - http://www.airsoftfo...gs-t104274.html, MechBox.com for the videos about how to disassemble/reassemble your gun and gear box, and Joel at AEX Oakland for helping me, free of charge, with a little issue that I will detail below. Thank goodness for the internet!
I decided to go ahead and just do it for the purpose of being able to fit various buckings on my Prometheus barrel (407mm); specifically, the Firefly bucking. Many people have had issues fitting the stock hop-up over most aftermarket buckings. Some people have had no issue. Unfortunately, I am one of the people that have had issues.
The hard part of this is changing out the air nozzle as you have to take apart the mech box to do so (it's important to have all the right tools and work space to do this...I won't go into detail as this is all on MechBox.com and I'm sure you can find a plethora of info on the web). However, this gives you a chance to clean it out, re-grease, and add a better o-ring on the piston; I used a x-ring from McMasters. It's basically an o-ring with squared off edges. Here's a discussion on that on Airsoft Retreat (you'll see that I participated in that discussion): http://www.airsoftre...p?topic=69098.0. Anyway, the mech box wasn't as bad as I thought as everything functioned normally (at this point, I did not shoot any BB's yet, just dry fired the gun to make sure everything sounds and feels right).
Anyway, yesterday I completed my disassembly and reassembly of the entire gun and fitted my CA TM M4/M16 hopup. I left the stock KWA BB feeder (part# 3) as the CA one didn't seem to fit as good. The hop-up unit actually had the axle for the middle gear snapped off, but I was able to super glue it back on and the gears seem to turn as good as it could. The TM hop-up fits a little tighter than the KWA one, but it does fit and it is not an issue, according to Joel at AEX Oakland, who says he has done this mod on many KWA M4's. I should note that before any of this, I fitted the TM hop-up over my barrel using a Prometheus bucking (soft). It fit just fine with just a bit of lube.
So I put everything together and fired a few test shots...nothing. Darn it! I spent the entire day making sure I did everything to a T, but the gun wasn't shooting any BB's. At this point, I decided to take the gun to AEX and ask Joel to help.
He tinkered around a bit and concluded that the problem was my flash hider. Because the 407mm barrel sticks out the outer barrel a bit (without the flash hider), the flash hider, when tightened all the way, will push the barrel back, causing to mis-align the hop-up unit and nozzle enough to where the BB's will not feed. The solution, for now, is to not tighten the flash hider all the way. Not too loose, but not too tight. Not sure how that will behave during a game - I'll report back. I think because the TM hop up is a tad bit bigger than the KWA one (read the part where I said it was a tight fit), it has this issue with the longer barrel. Those with a barrel that does not stick out, should not have this problem.
Hope this helps anyone who decides to do this "mod," if you can call it that.
Edited by Doctor Kajita, 30 September 2008 - 07:13 PM.