The reason for this L96 being a 650mm barrel is because it is a gas version, so the barrel can be extended back into the area usually containing the long bulky spring cylinder. As for more upgrades, I would advise you still grab a silencer and mod it to actually function; you could probably end up with a virtually silent rifle. I might get a higher end barrel but the madbulls are still nice. Another thing you could do is tap the magazine and hook up an HPA tank via air hose and 2nd stage regulator. I would double check on the moving parts that go from the trigger down to the pin hitting the gas chamber, make sure everything functions VERY smoothly and be sure to keep all those parts lubed properly to ensure the best consistency possible.