I'm trying the same with my AEG setup (G&G SR-25, with the stock brass barrel and with a 6.01x650mm too).
I'will use 2 differents hop up rubber (a stock one and a A+ rubber) with 0.25, 0.30 and 0.36g bbs for every setup.
I'will test the accuracy and range
So i'll post the result here when it's done.