Don't believe me? Fine, allow me to prove my point. Anyone who has done any shopping for tightbores on AGI has probably seen their "Tight Bore Barrel Test" video. If you haven't, it's embedded directly below.
The conclusion of the video is that 6.03mm tightbores do little to nothing in terms of improving accuracy, while 6.01's do a lot to tighten your spread. What AGI conveniently DOES NOT tell you is that KWA includes a 6.05mm stock barrel. In other words, the difference between the 6.03 and the stock barrel is a lot less noticeable than it would be if using a more common and less expensive model.
But why, you may ask, would they wish to make 6.01's look so much better than 6.03's? The answer is simple. Look at the price difference! They make a lot more money selling 6.01's, so naturally they're marketing them. Unfortunately, their "scientific" videos are actually fooling people - and not just into throwing more money around, but even to IGNORING or just plain not seeing the inadequacies of AGI's scientific method.
I rest my case. So please, next time you watch an AirsoftGI TV video, ask yourself: "Is this just a money making ploy? How much merit should I place in their results?" Remember, the best sources of unbiased information are blogs like this one or forums like ASF.