A question on relative parts

[Shutter]

I couldn't think of a better way to explain it in the title considering limited space, but heres the skinny.

The preface
I'm looking to throw [quite] a few dollars into my TM M4 over the winter season so I can have a decent field gun come spring. Its perfectly fine for CQB in its stock form, but I'd like to get a little more out of it when I head into the field.

The desired result
I'd like to take my gun up the 375-400 fps range for outdoors, and had the crazy idea of using the TM velocity reducer when I want to go indoors, all the while maintaining durability.

The problem
I realize that a single part on its own won't achieve my desired effect, and that many parts act together to affect FPS, as well as durability. I simply cannot just purchase a new spring on a whim and hope it works. To my knowledge, which is limited, I may be looking at, in a strictly FPS sense, a new spring and a tighter barrel.

Now, the true question that I'm getting at, with my desired FPS, what other related items may come up? A stronger spring requires a different battery, possibly a different spring guide? Pistons, gears, bushings, hopup, etc, etc all impact one another in a chain or "group".

I cannot realistically upgrade a single component without taking into consideration how all the rest of it will affect the end result both in overall FPS and durability.

Summary
What parts would you out there recommend to bring me up to my desired FPS, and in turn, what parts do they require be changed to maintain function and durability. What parts can be done in "groups" or "stages" to spread cost over time while not leaving me unarmed as it were?

While I realize there is no exact forumula for this kind of thing, I have heard things like, a tightbore adds 6fps, not to mention tighter groupings, and the spring comparison chart was also informative. If anyone has any usefull information, please post it.

[The Saint]

Well, a good start would be this: http://www.arniesairsoft.co.uk/?filn...1c/springs.htm

[gandar]

To go to 400fps, you should be ok with the stock gears, though looking at just a standard set of reinforced gears might not be a bad idea. I definately recommend a new spring guide, the metal ones with berrings are great. I'd also upgrade the bushings to metal bushings, and look at a good polycarbonate piston and aftermarket head. Tight bore is a great investment for accuracy. Your hopup should be fine. I'm running around 370ish I think in my AUG and I've got stock gears and motor, upgraded spring guide, upgraded piston, and I'm running a 9.6v 1700mAh battery, I'll be putting a tightbore on it when I have the extra money over the winter. Basically it runs like a top right now. Just make sure when you dive in to your mech box that you pay attention when you take it apart, and try to find a guide so you don't end up with shit flying everywhere and not know where to put it back in. Best advice with the mech box, if you do it on your own TAKE THE TIME TO SHIM IT PROPERLY! It is CRITICAL and will drastically affect your performance and mech box life.

Good luck man, look forward to seeing it.