5.0
Just played series 2002 with a new Excellerator 5.0. Good all round gun, the only problem I had was if you get any smeg in the bolt, after about ten shots it only half cocks, so you need to really keep it clean (not that I stayed in any of the games longh enough for that to make a difference!!). My FPS kept going up and up all day, but I'm running it on Co2, so thats not really the markers problem.
Apparently the feed tube is Locktite'd in, but I wouldnt know how to put it back.
One more word of advice: Planet are selling the 5.0 for £180, LPS (where I bought mine) £330. You do the maths!!