Introduction:The following information was posted in AirsoftRetreat.com Version 2. It originally included a review but I have decided to cut that part out in this revised version. The original ended up being a 17 page monster with many discussions going off topic (ie bignaz getting completely pwned) but it also contained lots of good info shared by other member's. If you want to read the original you can find it here on ASR V.2:
http://www.airsoftretreat.com/oldforums/topic.asp?TOPIC_ID=87937It is the longest(17 pages), most viewed(25115) and most replied(413) to thread in the whole LPEG section there(pats self on back).
This version will only include the Upgrade Guides from the original thread, the rest will be new or revised information with new/revised pictures. Heres how this post is going to be broken down:
Introduction
Brief Overview of the Stock BE Gearbox
Upgrade Guide: Stock Parts
Upgrade Guide: The Cylinder Unit
Upgrade Guide: The Drive System
Upgrade Guide: Hop Up Chamber and Barrel
Update on Upgraded BE Gearbox
Upgrade Guide: Bodywork
Upgrade Guide: Repairing
Conclusion
Picture/Video Gallery
Links and Information
Almost all of the gearbox information contained here is applicable to the BE AUG.
Brief Overview of the BE Gearbox:The stock BE box (both the XM8 and AUG versions) are copies of the Tokyo Marui version 3 gearbox with a few differences. The main difference is the fact that the BE box made of mostly plastic. All changes that BE implemented are mainly for cost savings:
- All plastic construction, only metal parts in the box are the springs, screws and gear axles.
- Non removeable motor cage.
- One piece cylinder unit vs. multi piece construction on the TM gearbox.
- Molded in bushings, non removeable.
- Additional two screws along the top of the gearbox vs. stopper rail on the TM.
- Simplified semi auto cut off assembly.
As a result of these changes the BE box is about half as strong as the metal version 3 gearbox. The stock TM V.3 gearbox shell can take up to 600fps without cracking, the BE's limit is about 1 joule or 328fps and I would put maximum reliable fps at about 300fps w. 0.20g. Contrary to popular belief the weakness in the BE gearbox is not the plastic gears but the plastic box itself. The two retaining nubs that hold the cylinder head in place are very small and connects to a thin area of the gearbox. When too much force is applied to them they will snap right off. I have been warning about this since I've first seen the BE gearbox and experienced the problem first hand after testing the limits of the BE box.
BE on the top @ 6.5 inches and TM on bottom @ 6 inches. Wire is slightly thicker and coild more spaced apart on the BE spring.
The stock version 2 BE XM8 shoots about 250fps out of the box which is about 30fps less than a TM AEG. The difference between the two is that the TM uses a softer spring to make more FPS and the BE XM uses a relatively heavy spring to make less FPS. The reason for this is because the BE gearbox is less effcient at pumping air and allows air to leak in many places. To improve the power without sacrificing reliability we will have to address the inherent ineffciencies in the system as a whole.
Upgrade Guide: Improving Stock PartsThere isnt much you can do with the stock cylinder unit to make it more effcient. One of the first upgrades you should do is regrease the cylinder and pistonhead with silicone oil. It's slicker than the original grease and provides good sealing. Doing this will increase the ROF and if youre lucky itll slightly improve the pistonhead/cylinder compression. Next thing is porting the stock pistonhead, this mod is a must for better sealing if you are planning on keeping all the stock internal parts. A stock AEG piston oring will fit in the BE cylinder unit but its kinda tight so I didnt run it like that. The stock oring is just a bit thinner than a AEG spring but its enough extra friction to lower your ROF.
This is how the pistonhead should look once youve ported it. It isnt hard to do and doesnt require special tools, you can do it with a hot nail and a pair of sisscors. Use the nail to make the holes and the sisscors to cut the rubber pad.
Even with the ported pistonhead, relubed cylinder and stretched oring the air nozzle will leak some air and something needs to be done about it if you want the best effciency from the gearbox as possible. I couldnt think of anything easily done that would help so I upgraded the whole cylinder unit and this brings us to...
Upgrade Guide: The Cylinder Unit*Upgrading any one part to TM spec'd parts will require upgrading other parts for correct fitment. For example, you cannot upgrade only the piston or pistonhead, you need all the other corresponding parts for the upgrade to work properly.*
The BE psiton is longer and has a shorter stroke(one less tooth) than the TM counterpart. To fit a TM spec'd piston into the BE gearbox is very easy if you arent upgrading to a metal gear set. If you plan on sticking with the stock gears all you need to do is get a TM piston or any piston made for a TM that has only one metal tooth and take off the metal tooth. You dont even have to cut anything just slide the tooth off or buy a Guarder economy piston which is what the piston should look like once youre done with it.
I know some of you guys may be asking why upgrade the piston when the problem is compression? Well the answer is simple, you cant just stick a TM piston head on a BE piston body to improve compression. As I mentioned earlier the BE piston is longer than the TM and simply slapping a TM piston head on would cause you to strip your gears if the gun is fired. Once the you have the correct piston you can mount the TM spec'd piston head on it.
BE to the left TM on the right.
The complete piston set should look like this.
With the new piston assembly you can now install a TM cylinder, cylinderhead and air nozzle. You cannot use the stock air nozzle with the new parts its wayyy too loose. Here are some helpful suggestions:
Cylinder - You will need a one made for the M4, its called a Type-2 cylinder if youre using a TM and a Type-1 if you buy Systema.
Cylinderhead - If youre using stock TM cylinderhead both the Version 2 and 3 will fit. For aftermarket you will want a version 3 AUG/G36 specific cylinderhead. It is the one with the longer nozzle tube.
Nozzle - If you get TM stay with a TM nozzle. For upgrade parts stick with the same manufacturer as the cylinderhead. For example, if you get a HurricanE cylinderhead get a HurricanE nozzle. You will need a nozzle made for the TM G36C.
This pic illustrates the amount of play the stock nozzle has on the new cylinder head.
The BE spring is wider than a stock TM spring and PDI aftermarket springs. Depending on the type of piston you choose to use you may find that the stock BE spring will no longer fit back into the piston (dont force and say it fits its gonna bind once you try to shoot it). To test the fit try to compress the spring (with spring guide on the end) into the piston, the spring guide should be able to touch the piston body. If it doesnt you have two options, bore out the hole in the piston to fit the spring or buy a new spring, I decided on a stock TM spring to keep with the effciency theme.
The spring guide is the only part you dont need to replace in the Cylinder Unit upgrade.
Spring guides from top to bottom: TM V3 for AUG/AK/SIG, BE XM8, TM V3 for G36c/Mp5K. Notice the molded in spacer. Both TM V3 spring guides will fit the BE box.
With these upgrades and the stock TM spring I am getting better power and range than the stock gun. The stock spring was stronger than the Marui but due to ineffciencies in the cylinder set you loose alot of that power. The upgrade I have installed has boosted the fps with no loss in ROF and zero loss of durability. Durability may be even better than stock cause
of the lighter tension spring.
Total estimated cost of upgrade is about 40-50$ depending on what you need to buy. For me it was free since all the parts are spare TM stuff from my parts bins.
Upgraded and ready to rock.
Upgrade Guide: The Drive SystemAlso known as the gears or drive train. Now remember what I said earlier about the limits of the BE gearbox, maximum reliable fps is at about 300-328fps. The stock gears will be able to take those power level easily, a set of TM gears will be able to handle up to 425fps but the BE gearbox can not. So is it worth it to upgrade the gears? Personally my answer is no, for the cost of a set of gears (even TM ones) and the time it takes to install them the gains are not worth it. I would rather buy a spare XM8 box (they are available now) than spend the money on metal gears. However if you still want metal gears or if you already have a set laying around that you want to install here is how to go about it.
There are two ways you can run metal gears. With the stock BE cylinder unit or with a upgraded TM cylinder unit(the upgrade shown earlier).
Metal gears with stock Cylinder UnitWhat you need
-Metal Pinion Gear,
-Metal Gear Set
-Shims
-File or Dremel tool
First take the stock plastic pinion gear off and fit the metal one on. Take the sector gear and dremel off the largest tooth. This will correct for the shorter stroke and is actually a modification some people do on high rof guns to prevent the gun from stripping pistons (
http://pageproducer.arczip.com/daedalus03/speed.html) sector gear will be weakend if you are using a stock tm gearset, for aftermarket gears there wont be any durability issues since all teeth are the same thickness. BE piston will be under more stress because of all plastic construction riding on metal gears.
Dremel or file this fatter tooth down flat.
This is the low cost way and doesnt require replacing the whole cylinder unit, only the drive system is changed.
Metal Gears with Upgraded Cylinder UnitThe second way is more costly but is the better option if you want metal gears. It requires replacing almost the all BE internals with TM spec'd internals. Heres a list of what you'll need
-AEG metal gear set
-AEG Pinion gear
-TM spec'd cylinder unit (complete with piston, pist.head, cylinder, cyl.head, nozzle). spring guide and tappet plate could be -reused, the tappet plate is under more stress so that would be a higher priority item than the spring guide. Youll need a normal AEG piston with all the teeth intact. If you did the cylinder unit mod I posted earlier youll have to put that metal tooth back on or find one. Stock TM piston reccomended, they are good up to 400fps and I dont think the BE box should be upgraded anywhere near that so its strong enough.
-Shims
Upgrade Guide: Hop Up Chamber and BarrelThe BE hop up chamber is a modified copy of the TM G36C part. The changes are small but enough to make the two parts non interchangeable. You will lose fps if you change the hop up unit for a TM one. This means that we are stuck using the BE chamber which is not great but can be improved upon. To bring it up to TM-ish standards there are a few issues that need to be addressed.
BE Version 1 hop up unit compared to the TM G36C hop up unit. The BE Version 2's are reported to have black hop ups.
To improve the stock hop chamber the first thing you will want to upgrade is the hop up buckings. The stock parts are poorly made, fragile and easily torn/ripped when changing to a new barrel. I would reccomend upgrading to something like a TM stock bucking set or a Guarder set, you dont need the expensive KM, Prometheus or Firefly buckings but if you can afford it they are better. A new set of bucking will help out with the responsiveness of the hop up and air seal.
The BE hop unit has a shorter arm and that results in less hop up, you have to turn the dial very high to get a good setting(at least on my gun). There are a few easy solutions to the problem but I decided to do a more complicated modification.
The modified solid v-hop up arm compared to the TM G36C.
Different view of the v-hop mod.
Completed v-hop modification.
As I said earlier there are easier ways to get more hop up at a lower setting. One way is to simply shim the round bucking.
The hop chamber can be improved but the barrel is a differnt story, the thing looks like a mess. Cheap materials and bad construction practically guarantees youll end up with a sorry barrel. I suggest changing it out as soon as you can. A stock TM, cheap tight bore (ie. Systema, Madbull etc) or even the SRC M4 barrel will do wonders for your accuracy and will provide a fps boost. To fit a longer M4 length barrel you will need to modifiy the flashider so that the barrel can pass through.
Stock barrel hop up cut out. Very uneven cuts and scratched inside the barrel.
Shave the inner right angles so that the barrel is able to clear the flashider prongs. This modification is also reccomended to all BE XM8's even if you dont intend on upgrading the barrel. The stock flashider prongs interfer with the bb's when the gun is being shot. The bb's hitting the flashider will cause irratic shot dispertion and your accuracy go down the drain.
The TM M4 length barrel is longer than stock and some of it will show through the flashider.
Here is a reference photo just in case you forget how to put the hop up back together. The unit pictured is from a G36c but the BE takes down and assembles exactly the same way.
Update on Upgraded BE GearboxI've lost count of how many rounds have been fired from this gun but it is a good amount. My gun has been upgraded with many different set ups including a 350fps tune up which lead to the destruction of one of the cylinder head retaining nubs.
The gears after about 4 months of use with various upgrades up to 350fps. They still look good and dont have much wear on them at all which is surprising. Quality of the installtion of the upgrade is important to the overall durability, if you install the upgrades carelessly your gearbox could fail much earlier.
The damage to the cylinder retaining nub. On my gun both sides are broken, the gun will continue to work with both nubs gone but its better to fix them.
Upgrade Guide: Bodywork
This section will focus on what I did to make the BE XM8 look more realistic. Other misc body work such as making the XM8 accept TM/Ca G36c mags will also be included here. I wont get into too much details about these mods, you can figure them out yourself easily. FOr the mag mods there is a easier way to do it and its detailed here:
https://www.evike.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=W&Product_Code=AEG_BE_XM8&Category_Code= at the very bottom of the gun description. There is another method posted here in the old LPEG section:
http://www.airsoftretreat.com/oldforums/topic.asp?TOPIC_ID=91866&SearchTerms=XM8,G36,mag
diagram by ZGMF-X20A of the Filipino Airsoft forums. Image has been cropped.
Magazine comparison. TM to the left and BE at right.
Reference photos of the improved XM8(real steel).
Rubberized buttstock.
Rubberized handguard.
The product I used:
http://www.duplicolor.com/products/undercoating.html 
Painted OD with Krylon Camo Paint.
Painted PCAPS.
or maybe its the tm hop unit and barrel.
