Enhanced airseal on the G36...

[cjfield1129]

After much troublesome labor to pinpoint FPS loss on my G36, I did something right. I wanted to post my mods in case any other G36 users had similiar issues. I will note that any modification is done at your own risk. I did the mods with extra parts available as a fail safe.
The main issue stemmed from airseal between the hop up unit and the mechbox. I knew that the mechbox internals were air tight due to numerous tests. The lack of airseal btw the hopup unit and mechbox was confirmed. When I fired, I would pull back on the barrel towards the mechbox and see as much as a 50 fps increase. Otherwise it was just shooting 330 with a PDI 170 spring.
To make the long story short, I did the following modifications. I shaved off the two tabs on the hop up that lock the barrel & hopup into the front assembly. I then shaved a small bit off the two walls of the rear portion of the hop up unit that rest against the mechbox. These two mods would allow the hopup unit to sit slightly closer to the mechbox. I also realized that the Aug sized air nozzle created the best airseal (b/c it was slightly longer). The Guarder Aug nozzle created a better airseal than both the stock G36 nozzle and the Guarder G36 nozzle. A picture comparision can be found here: http://i19.photobucket.com/albums/b1...sAUGG36G36.jpg
I tried a KM RH65 bucking but didn't have the best luck with feeding and airseal. I may try it out again later but things are working perfect right now and I don't want to touch anything. I am currently using a Guarder clear bucking. In order for this bucking to get the best airseal though, I had to insert the brass collar/ring into the hopup unit -similiar to what you would do using the nylon collar from the RH65 bucking. With the brass collar in place, hop up unit reassembled, and Aug nozzle installed, I am now getting 415-420 average FPS -again with a PDI 170.
For airseal reference, I am running the following upgrades: KM tightbore 534mm, Prometheus piston head w/bearing, Systema NB cylinder, Prometheus Aug cylinder head, Guarder Aug nozzle, and Systema metal spring guide w/ bearing. Hope this helps anyone experiencing similiar airseal issues with their G36.
I will take a few pics the next time I have the hop up out. For the time being see: http://i19.photobucket.com/albums/b1...r-g36_big2.jpg

[freeman]

Is your G36 made by TM or CA?

Is Aug cylinder head necessary to use Aug air nozzle?Can i just use the Aug nozzle with normal Ver.3 cylinder head?

[HaZarD SFD]

This mod is very interesting as im using a Prom MS110 in my G36C.. and if you could
take some more in depth pictures this would be great.. I have noticed some air pressure
being released form the magwell when I put my finger near the bb port.. and wondered
how much FPS loss I was getting from lack of seal..

[cjfield1129]

Originally Posted by freeman

Is your G36 made by TM or CA?
Is Aug cylinder head necessary to use Aug air nozzle?Can i just use the Aug nozzle with normal Ver.3 cylinder head?

It's actually made by Star. I wanted the quick spring change feature their gearbox uses. The Aug cylinder head is not necessary but helps aid in better airseal. I think that as long as you use an air nozzle that has an o-ring on the inside to prevent air loss, you should be fine. It would be more of a problem if you were to use a stock Aug nozzle. In that case, the air loss would be more dramatic. The Aug cylinder head is about 10mm longer than the standard V3 cylinder head (AK47, etc).

Originally Posted by HaZarD SFD

This mod is very interesting as im using a Prom MS110 in my G36C.. and if you could take some more in depth pictures this would be great.. I have noticed some air pressure being released form the magwell when I put my finger near the bb port.. and wondered how much FPS loss I was getting from lack of seal..

Out of curiousity, if you have a chrono, gently pull back on the barrel (towards you) while chrono'ing the gun. If the FPS goes up, you have confirmed your problem. In my case the gun jumped a good 35 fps to where it should be. I installed and reinstalled the hop up unit and the bucking numerous times but that did not solve the problem. It was not until I did the mod to the hop up that the FPS went up. I don't have any pics of the modifications b/c you cant really tell by the pictures. I do have one reference picture that I use for clarification on the mods which should help. Let me know if you have any further questions.

[Imperial Guard]

Approximately how much plastic should be filed off?

[cjfield1129]

I filed off about a mm or so. Start with just the locking tabs. That alone may get the hop up unit closer to the gearbox by itself. If you still get higher fps when you test by pulling the barrel back towards you during chrono, then you (like I did) could then file a tiny bit off the rear of the unit. Be careful. Too much will cause feeding problems.

[MMMiles!]

You shouldn't be able to pull back on the barrel in a CA or TM G36 (it's fixed into the metal spine that runs the length of the gun, that the mechbox is also keyed into).

It sounds like STAR has fitment issues. Given how good the CA and TM G36 models are... I can't think of a good reason to go with a company like STAR with a mixed track record on internals.

[cjfield1129]

Even though you can't feel it, there is still the ability to pull it back. Yes you are putting tension on the tabs but it serves to tests the airseal btw the nozzle and the hopup unit/bucking. In my case, the unit needed to sit a little closer to the mechbox for optimal airseal. Other manufacturers may be better, but it is an easy test. My thoughts on getting the Star were this: I would still have upgraded the internals if I got the CA or TM version. The big question is if you are going to leave it stock. The shabby internals argument, though arguable, is a mute point in my case. I also really wanted the quick spring change feature for swapping springs on the fly. I'm pleased.

[Skruface]

Originally Posted by HonestJohn

Given how good the CA and TM G36 models are... I can't think of a good reason to go with a company like STAR with a mixed track record on internals.

I bet you thought you'd never be saying that, eh Miles? :razz:

[MMMiles!]

Originally Posted by Skruface

I bet you thought you'd never be saying that, eh Miles? :razz:

I know eh. I still prefer the TM over the CA, but for the K and E it's hard to say the CA isn't worth it. And I won't get started on armalites: CA isn't perfect but it sure is appealing.

We've cracked open a few mechboxes now, and CA internals look quite good - and pretty much all the drawbacks (CA's are just missing the subtle refinement you find in japanese guns) I could think of are offset handily by improvements CA has made to the mechboxes (metal bushings, ported piston head, piston head nut/loose spring). I think we'll do a comparison review sometime soon.

[swatt13]

http://i19.photobucket.com/albums/b1...sAUGG36G36.jpg

pic isnt working (yes i know how old this thread is) could you repost pic, i need it now lol.

[cjfield1129]

http://i19.photobucket.com/albums/b1...sAUGG36G36.jpg

[swatt13]

thank you.