Any AEG gun you put a higher rated spring into needs to have metal bushings installed. This is because the stock bushings are plastic and can't take the higher stress from the upgraded spring. This also entails re-shimming the gearbox which is the hardest thing to do properly. I highly suggest either having a professional do this for you, or at the least have somebody who's done it before teach you how it's done properly. On a side note, running a 9.6v battery in a stock AEG isn't a good ideal because it can heat up the stock plastic bushings too much and melt/deform them.
CA, G&P, G&G, and ICS/AE already have metal bushings and don't necessarily need new ones for an upgraded spring (although remember high-quality aftermarket parts are almost always better than stock). *some of the older G&G and ICS guns still used plastic/nylon bushings.
GEARS: TM and CA stock gears are usually perfectly fine for up to 400 FPS when shimmed correctly. But of course I would rather pay for a set of gears and be set for the long run; especially if a professional is doing the upgrade for you. Buying aftermarket gears will last much longer at 400 FPS than stock gears/
I don't recommend ALUMINUM piston heads and pistons. It doesn't flex. It's heavier so it hurts the gearbox more. It lowers your Rate-Of-Fire. It can break gearboxes with high FPS set-ups (especially the M4/M16 gearbox).
330 FPS
To upgrade a gun to 330 FPS I would feel comfortable with just installing metal bushings, and a 330 FPS spring. I always recommend a PDI spring; and some people say a PDI spring works better with a metal guide rod with bearings so it can twist and turn freely.
330 FPS is also the highest recommended FPS for a high-speed upgrade; you may be able to push it to 350 FPS but of course that will lower the ROF and put more stress on the gears and bearings. Your gun will shoot faster by installing what I mentioned above, and a 9.6v battery (or a 10.8+ battery at your own risk). To do it the proper way you need to install high-speed gears with bearing bushings* (bearing bushings have ball bearings in them to spin faster), and a 9.6v battery. A Systema high-speed motor is always a nice touch. ---but since this gun will be shooting so much faster, to increase it's longevity I would upgrade other parts as well (Spring guide, piston, piston head, everything really)
350 FPS
A 350 FPS can be achieved by installing what I said above, but instead using a 350 FPS spring.
But, I always recommend replacing the guide rod, spring, piston, piston head, to be safe.
400 FPS
You can of course, just install metal bushings (if needed), and stick in a 400 FPS spring, but that's running the risk of destroying your gearbox, and something may break in a not-so-long time period.
So, at 400 FPS, the bare minimum I would get is:
Metal Bushings
Spring Guide with Bearings
Spring
metal shims
9.6v battery
Optional:
Nozzle
sector chip
450 FPS
This FPS limit is only for those who can work on their own guns; since your gun will most likely be breaking more often than you thought possible. This person has a large pocketbook, and many spare parts on hand to replace those that break every couple months or so from frequent games.
Many people recommend a re-inforced gearbox.
metal shims
metal spring guide with bearings
metal bushings
air nozzle
spring
sector chip
new gears
HOP-UP
Hop-up has to be the single most important part of your gun that makes it shoot good (along with a working mag to load the BB's into the hop-up). If the hop-up isn't working properly, it doesn't matter how many upgraded parts your gun has, or how much FPS, it'll still shoot horribly.
BARRELS
Some people believe the $50 you'll spend on a tightbore barrel isn't worth it in performance. Some people also like the full-auto small 'shotgun' spread of the shots at the end of your range since you're more likely to hit your target that way.
Personally, if you have a smaller length barreled gun, below say M4 (363mm) length, I would get a tightbore barrel to compensate for the length. 363mm and above I think is perfectly fine with the stock barrel ---but then again I have a 6.03 Prometheus barrel in my M4 (which for the record has a horrible 10,000 to 20,000 shot break in period), since I wanted every single available part, and the biggest thing I notice about it is a slight increase in FPS.
BARREL LENGTH / CYLINDER
I wanted to touch upon this subject a little bit. If you get a massively longer inner barrel than your original gun has, you'll need to get a new cylinder. This is because the cylinder is matched to the length of the barrel. So if you just put a M16 length barrel in your MP5, you'll need to purchase a M16 cylinder to maintain the correct FPS.
BATTERIES
I recommend a 9.6v battery, which will fit into almost any gun (even a MP5K with slight modification). I recommend this because when you raise your FPS, your gun shoots slower; and a 9.6v battery will make your gun shoot at, or above, the rate-of-fire your stock gun had. If you still want to use a 8.4v battery in your upgraded gun, I would make sure it's above 1400mah (4/5A or larger cells), be prepared for a slower shooting gun, and make sure the gears are shimmed perfectly.
10.8 volts and above batteries can be used, but keep in mind the motor is only meant to work on 8.4 volts, so you're risking burning out the motor, and you might as well get better wiring for the gun as well. Also, at 10.8 volts your gun will wear out quicker since it's shooting more shots in the same period of time, as well as the switch assembly slowly getting corroded from the arching of the 10.8v battery.
BRANDS OF PARTS
Systema has long been known to make some of the best upgrade parts. I trust everything they make but their pistons (which have had problems in the past, but are most likely fixed).
Prometheus makes excellent quality parts. Many people regard their gears as being the best; along with their 6.03 tightbore barrels (which have a break-in period as I mentioned above).
Guarder parts are also known to be high-quality, but there's a warning on their polycarb piston heads being defective right now (12/06).
Most upgraders use PDI Springs because they're supposed to put less stress on the gearbox than other springs because of how they're wound. I have no clue how the physics behind this principle work, but I trust the Airsmiths know what they're talking about.
I like the stock TM motor because it'll last basically forever. It's like a Honda Civic; it doesn't have the performance of a Porsche, but it'll last much longer. Systema motors are good, as well as Eagle Force.
PARTS COMPATIBILITY
I'm talking about version 2 and version 3 gearboxes here which are the most popular.
Gearbox version specific:
Spring Guide
Tappet Plate
Cylinder head
Gun Model Specific:
Nozzle
Selector plate
Wiring harness (wired to the front or back)
Cylinder (matched to inner barrel length)
Interchangeable:
Spring
Piston
Piston Head
Gears
Bushings
Motor
Anti-Reversal Latch
Mon Sep 24, 2007 10:03 pm