A decent low cost linear steel spring from ZCI. These come in a plain plastic bag. The M100's are very accurate, always test around 330 FPS with 0.2g.
Spring ends are flattened, providing better contact area.
M100 = 330 FPS with 0.2g
When a new batch of springs arrive I generally test one of each power, however occasionally springs may get put into the wrong packaging at the factory. In cases where FPS is wildly different to that advertised we offer a free returns service so that the spring can be tested and an adequate replacement be sent out. When fitting and testing springs yourself please remember to test using the correct cylinder and inner barrel length combination.
When a new batch of springs arrive I generally test one of each power. Below is the setup I used for this particular spring:
Good cylinder, cylinder head, piston head and nozzle compression
Hop set off
Bearing on Spring Guide
No Bearing on Piston Head
No AOE correction
340mm ZCI inner barrel
ZCI plastic rotary hop chamber
ZCI 60 degree hop