Technical information

Practical A.E.G Upgrade 2006

What is wrong with a custom made spring?

Systema Springs versus PDI Springs

Many people believe that custom made springs are no good for AEGs. In fact, the

quality of a spring depends largely on the built material as well as the

workmanship of the spring shop. If you go to a good spring shop, chance is that

you can get a tailor made spring as good as those offered by Systema and PDI.

If you buy a Systema (or PDI) spring, you know at the time of purchase what FPS

can be achieved. Their products are proven. With a custom made spring, you

must measure the FPS and may have to do fine tuning on your own.

Systema springs are in general longer and harder, while PDI springs are shorter

and a little softer. Both of them are from Japan and are of similar prices. People

prefer PDI springs because PDI springs are thought to be less stressful for the

gears. Do note that PDI springs are wider than Systema springs and are

therefore not compatible with certain pistons (such as the Prometheus Hard

pistons). The harder Systema springs tend to fracture, thus causing

disintegration and mechbox lockup. PDI springs, on the other hand, are more

reliable in this regard.

Based on our experience, installation-wise PDI springs are much easier to deal

with. Below is a table for your reference:

Systema PDI approx. equivalence FPS with 0.20g BBs

M90 100% 295~300

M100 120% 325~340

M110 150% 365~380

M120 170% 390~400

M130 210% 425~440