[Flatlander]

Stalker, are you using those purple, transparent modify pistons? I was not impressed with the one (and only mind you) modify piston I've come across. Set up: modify piston, piston head and I believe modify m100 spring. After about 200 rounds the piston had like a spider crack going almost the entire length of the piston. Good thing the gun was giving me grief and I caught it before it exploded inside the mechbox, haha.

EDIT: I put a deepfire nylon piston in a buddy's m249 running a 170% spring (m120 equiv. roughly) and after around 20k+ rounds it was looking in great shape. I also remember reading on airsoftmechanics that it was one of the highest hardness tested nylon pistons around.