Mine was running at battle rifle power levels out of the box, so I'd be surprised if you get stuck with a MED . Mine is the S&T , other brands may be hotter.
Assuming yours is the S&T also , then mine is set for .30 BBs and lifts them easily on the stock hop . I would highly recomend changing the spring (again if it's the S&T) as the one they come with is horrible and kinks up inside the bolt.
If Survival airsoft is the one at Torrington it's my local site and very good. Decent bunch of folk there, very friendly and although people play hard, no one takes it too seriously . Used my Lee Enfield there 2 weeks ago and had a blast running it as a battle rifle.