Internal Spring Upgrade Help

[21cubs]

Hey guys, long time no see! I have been in Ohio for college this past school year and miss TN airsoft quite a bit. Anyways, I have had my KWA KM4 RIS 2GX for a little over two years now. I've played about once a month since then. My spring, I feel, is becoming slightly weaker than where I want it to be. So, do you guys have any suggestions on the best brand to put in my KWA for optimal performance and quality around the 400 fps mark?

Thanks!
21cubs

[Lancer]

In terms of spring technology, there isn't a ton of difference between manufactures. My only advice is stay away from Madbull springs, as I have had issues with them being slightly thicker and not being able to fit into pistons when they are fully compressed. Other than that, any old M120 should be totally fine (and should get you over 400 fps, if you do your compression right).