[Scallene]

Base: Ca-25
Objectives: 275' Torso, consistent, quiet as possible

Purchase Parts:
Madbull v2 509mm
Systema AUG nozzle
Bravo Aluminium Cylinder head
Bravo Aluminium Piston head
Bravo Poly carb piston (10 steel teeth)
Scs Nub
Piston spacer

DIY mods
http://www.airsoftsniperforum.com/43-longrange-aegs/892-holy-grail-building-your-dmr-aeg.html
Stuff extra body parts with foam

Will this do the trick?

 

[Pinguiclia]

Systema AUG nozzle
Bravo Aluminium Cylinder head
Bravo Aluminium Piston head
Bravo Poly carb piston (10 steel teeth)

All these parts aren't really needed. You said you only put a few hundred rounds through the gun so your piston isn't going to be chewed up to much, with the right shimming and since you're cutting your spring the stock piston should do. As for all the compression parts there are plenty of DIY mods you can do to get near perfect compression with stock parts. It's all about saving money!

 

[Madsvg]

See if you're able to get an R-hop in it. That'll stabilize it quite a bit and increase your effective range.

Other then that I have to agree with Ping

 

[Scallene]

A few of these parts are necessary/optimal replacing the piston with a normal piston and using a spacer from lowes 10mm is like short stroking your piston, this will speed up your trigger response by a good deal. The nozzle on this gun is gonna be glued in so you want a nozzle with o-rings so you don't have to buy a new plate. The piston and piston head probably are not needed so I agree with you there.