Keep your upgrades as simple as possible; follow the upgrade guides already posted.
Do not change anything that is not broken.
That is the best course of action.
Only start changing other parts as they break or when you know how they work 100%.

yes i agree but i want to be able to shoot with a 0.25g bb. the only problem is with my current speed they take there sweet ass time to go any were. so with i tighter barrel i will gain tighter groups also. i just want to know if 6.03 is too tight. or should i go with a 6.04?

Changing the motor won't make your BB's get to the target faster. A tightbore barrel will add 8-15 fps in my experience if it's the same length as your stock barrel....that's not enough to notice a difference in the time it takes your bb's to reach the target (roughly 2-3% on a 400 FPS gun).

no i know but if i use i higher tourque engin i can get away with a higher powerd spring. i want to bring my gun to 400fps in the end. i plan on geting a bore up cylender kit from systema and perhaps a 120pdi spring. but i want to know if a 6.03mm barel is to tight, as in will i have problems with bb's jaming n such. i would also like a slightly longer barrel. i plan to conseal it under a silencer. i would rather optimize my gun for maximum eficiency to get a higher FpS rather than just over powering it. sure i can trow in the highest touque engine available. but if i can avoid it. then whats the point. its just that i would have thoes 2 engins availible to me is all.

in the bitter end i want 400fps with a 0.20g bb with the tightest groupings posible at 40 yards. i dont know what the fps on a 0.25g bb would be though. i am not overly concerend with RoF

What we are saying is that you obviously dont know enough about upgrades to make a smart choice, and you are doing this in a very complicated (and expensive) way.

All you need, and nothing else, is a decent spring and metal bushings if your gun does not already have those. Period.

Then, like many, you must remember that 400fps is NOT a GOAL to achieve, but a maximum LIMIT. There is no contest to reach that number, no race, no prizes.

All the information you need is posted, even pinned, in this section. Please read it.

No AEG will give you decent groupings at 40 yards. If you can get 2" groups at 30ft, then you should be able to hit anything (remember, we're going for man sized targets at any given range and it only takes a BB or two hit to make the guy call himself out; case in point, my MP5 shooting around 370fps does the 2" groups, and have gotten most BBs on target out to 150ft away.)

I say you get your tightbore (6.03mm is fine, using quality ammo and keeping it clean will reduce if not eliminate any chances of jamming, remember that the biggest BB sizes measure around 5.92-5.94mm diameter, so that gives you 0.07-0.09mm clearance with a 6.03mm barrel), buy a Prometheus 110 sping (should put you around 360fps roughly) and a bearing spring guide, total fps should be around 385-390 fps, and gives you the wiggle room to constantly stay under 400fps. Some places are pretty tight about fps, I've seen guns that, out of 10 shots, 2-3 might be 403fps, be given a conditional allowance to play that one game day, sometimes even only set to semi. The best tuned guns out there will be off in velocity by +/- 3 to 5 fps, so don't bother screwing around trying to get 400fps on the nose, it's pointless. As you can see with my MP5 example, one doesn't NEED to be at 400fps to work right with 0.25g BBs. Mine has minimal upgrades, and outshoots most other AEGs.

im sorry i dont think i made my self understood. its not that i want to hit the cross hair of a scope every time at 40 yards. but hit a torraso at that distance. 400fps i didn't mean as a goal but as a limit of what i want my uprades to go no farther than. although i would like to push a 0.25g bb at 300fps i just want to optimize my gun to be the absolute best it can be without burning a motor or breaking a gear box.

CDN_stalker i apreciate your suggestions. i think you realy helped me out. i was un aware of bbs going no farther that 6mm. i though they would be if any thing larger not smaller. what metal do u sugest i use for a barrel.? thanks

Suggest yo ubuy a Prometheus 6.03mm barrel, they are made out of stainless steel and come very highly recommended by many. Just keep it clean and you'll love it.

sweet thanks.

Does some of the things mentioned in this guide apply to BA snipers as well?...or is it AEG exclusive?

This thread is second only to the "How to get age-verified" thread on ASC in terms of awesomeness.

honestly - I don't even have an aeg yet, but I read every single word of your post...and then bookmarked it.

You basically answered 8 of the 10 top questions I was going to ask!

I know it's long after the fact; but thank you so much for writing this!

This guide was written for AEGs. BAs function differently - first of all, they're not electric, so the system is completely different.

About the only similarity in basic function would be the cylinder, cylinder head, nozzle, piston, spring guide and sp ring, but beyond basic function, they are completely different from AEG parts as well.

ha ha i just bought a TM M4 and i was reading this and got lost i guess it takes time and paitence to understand.

To be honest, this probably needs an update. It's more than a few years old and there are tons of newly designed parts that are more commonly available, and some that are completely off the market.

Howdy! I just want to share my upgrades for my AEG's

CA SLR105 - 550ish fps (yes we do have open fps game sites here in the Philippines)

Systema m150 spring
Techpro Piston Head Double O-ring with Bearing
Systema Spring Guide With Bearing
G-Factory ported Aluminum Piston Body Half Tooth
Guarder Infinite Gears
Guarder Red Motor
6.03id Tight Bore Barrel 455mm
Systema Hop Up Rubber
Bhremen Haus 15c 2000mah 11.1v Lipoly Battery
Stock Cylinder Head and Tappet Plate


JG Spetsnaz - 450ish (Legal FPS for most sites)

Pdi 190 Spring
CA STU Gears
SRC Piston Head With Bearing
Systema Spring Guide With Bearing
Deepfire Titanium Piston Body Full Tooth
Guarder m4 Length Air Seal Nozzle (AK nozzles are 1mm short)
Marui EG1000 Motor
Stock Cylinder Head
6.03 Tight Bore Barrel 363mm
Systema Hop Up Rubber
Bhremen Haus 12c 1600mah 11.1v Lipoly Battery

Cyma AK74U - 390 - 400ish FPS (Some CQB Sites)

Stock Springs
SRC Spring Guide With Bearing
Marui EG1000 Motor
Systema Hop Up Rubber
6.04id Tight Bore Barrel 301mm
Stock Gears, Piston Body, Piston Head (Cyma's have strong stock piston bodies)
Sector Chip
GE Power 12c 1300man stick type 11.1v Lipoly Batteries


CA M4a1 Compact Seal - 390fps

m120 Spring
Systema Hop Up Rubber
CA Air Seal Nozzle
6.03 id Tight Bore Barrel 229mm
Deepfire Polycarb Piston Body
Noveske Amplifier Flash Hider
11.1v Lipoly Batt 1250mah 15c
Stock Everything Else (comes with stock spring guide w/ bearing, piston head w/ bearing, Thanks CA!)

The reason why I do upgrade my AEG's?? Because I play various scenarios on various gamesites with various FPS Limits. Sometimes i do assault with my Spetsnaz which by the way is my favorite gun because of its versatility in the field, or i do Sniper duties using my CA SLR, or do suppresing fire using my CYMA 74u on CQB Sites, or do quick room clearings using my Compact Seal. I do love my AEG's!! They serve me well. :)