An airsoft gun is only part of the equation, the user, his targets and venue variables make up the rest.
I find my stock KJ M9 runs as reliably as my heavily upgraded hi capa in certain scenarios.
That being said I can bag twice as many kills with cold steel trainer knife as I could with a BB in certain scenarios. Fancy upgraded guns are great; however only just a part of equation. If a user is competent and understands their playing venue and knows the limitations of their existing airsoft gun then they can perform accordingly to the situation. Not to downplay the notion of upgrades; I'm just stating that they are not always required.
"Its only a little bit on fire"