Honestly it's probably easier to get 2 guns. I know it can be cost prohibitive at the start but at least you're not constantly swapping the springs in and out when you go from indoor to outdoor and constantly opening the gearbox is never a good idea.
A gun with a quick change spring/upper (eg. Ares or ICS or a SystemA PTW if you can front $2000 for the gun and cylinders you need (black and blue/gold cylinders)) could be a choice but then again it's still easier at the end of the day to get 2 guns.
For now get an outdoor gun and buy a cheapo Aftermath with the intention of running that as a CQB gun. The innards of the aftermath are pretty solid, just the externals are a bit "meh" but downgrading to an M80 or M90 spring to lessen the wear on it and making sure you're under CQB limits is good enough for the short term until you decide to buy another "better" CQB gun. Also note that the difference between 270 FPS and 330 FPS isn't that much when your target is like 20-30 feet away at most. It's fractions of a second difference in time to target if you do the math.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE