JESUS. I leave for a week and this happens??
There are no traditional rifled barrels for airsoft rifles. It just doesn't work like that.
The TK twist barrels are hit and miss, but offer decent performance for there intended FPS.
The FALCON grooved/"rifled" barrels offer much better performance at all fps, especially when using the falcon bucking.
The long range barrels found in gas classics are still some of the best range runners on the market.
SO_
6.01mm Barrels are good for adding FPS, but they actually decrease over all accuracy.
6.03mm Barrels increase overall accuracy, and add a very minor fps increase
6.05mm Barrels are the most consistent, but sacrifice the last 30' or so out of a 6.03, they are widely preferred for spring snipers, and lead to a glide type trajectory.
That said, brand is much more important then size with anything above 6.03, a 6.05 Prometheus will rock the socks off a lower quality 6.03.
This all relates to the theory of the air cushion. That is, that an airsoft pellet does not touch the sides when it travels down the barrel, and that each of the touches adds a different angle/slows the spin, generally makes it less accurate, hence the hate for 6.01. The amount of air around the pellet is theorized to be the controlling factor in the accuracy and consistency of the shot, IE, the pellet is propelled on a cushion of air. The shot is more accurate, but more air is wasted in a wider barrel.
So in short.
Reaps does not work, and is a marketing gimmick.
Falcon red and green buckings work, and are great
The Rhop is the way to go.