Even though I have many years experience on the TM MP5s, I don't feel like typing.
What I will give you is this: Get a Modify 100 and it'll guaranteed give you close to 350fps, might net you 360fps, but all depends on other upgrades going in the gun, and how the air seal is on the parts already installed (might have a +/-20fps).
CA springs........... who freaking knows, they could end up being worse than PDI AEG springs (350-425fps for the same rated spring).
Watch out though, you are likely to crack the mechbox in short time after knocking it up. Mine broke within two months of shooting in the basement (few mags per night) after upgrading my SD to 350fps. What you might consider is installing a tightbore of 330mm length, I did to mine and got a 20fps increase. And try out a couple different brands of hop up rubber, piston head, nozzle, etc. Best way to upgrade is to use better BBs, and focus on airseal, then go for a heavier spring if all that is done and you still want a bit more. Will reduce the rate of wear an upgraded AEG goes through too.
Last edited by CDN_Stalker; February 7th, 2011 at 22:15..