With the proliferation of so many AEG main springs available to choose from nowadays, it is not so simple to pick a spring from either SystemA or PDI.
Now there are springs by SystemA, PDI, Guarder, KM (Head 1950), Prometheus, Top Power and Angel with many more to come.
After many hours, of swapping, testing, shooting and recording, I have finally come up with a new spring chart.
http://www.airsoftcanada.com/SpringChart.html
Although not 100% complete, the chart is very near completion and thought that I would post up the results now and will update it as I come across new springs and results.
Enjoy.