M4 spring upgrade from stock
 

I'm thinking of upgrading my M4 to around 320-330 fps. The parts I'm thinking of using are as follows; SP100 spring, Guarder steel bushing set ver.2/ver.3, Guarder Shim Set. I assume my ROF will drop if I still use my 8.4 battery, should I go with a 9.6? The white grease and silicon lubricant I have in my garage, the stuff is from Crappy Tire. Is this setup ok or am I missing something important stuff?

8.4 should be able to handle that upgrade fine, although ROF will be a tad noticeably slower. It's not necessary to go to 9.6v.

If you're going to use "teh white grease from your garage from Crappy Tire", make sure it's white lithium grease. And don't use that silicon lubricant - it has petroleum distillates in it.