When an bb travels through a 6.01 barrel, it has to push the air in the barrel forward, thus giving it less fps, also it sucks in air behind the bb creating a sort of turbulence which causes it to be less accurate.
If a bb travels through, let's say, a 6.03 barrel, the air that pushes the bb forward also pushes the air in front of the bb forward, giving the bb less resistance from the air it has to push forward because there is very little left. It won't have to suck in air behind the bb aswell because there is a space between the bb and the barrel (this space should be 0.08).
You should check what size your bb's are, just because it says 6 mm doesn't mean it's 6 mm.
Most companies make bb's that are 5.95-5.97mm. So a 5.95 bb would need a 6.03 barrel to get the best performance. A 5.97 bb would need a 6.05 barrel etc.
I read this somewhere but can't remember where, if there is someone who knows what I'm talking about but can explain it better, please post it to make life easier
Anyway, hope this helps.
If a bb travels through, let's say, a 6.03 barrel, the air that pushes the bb forward also pushes the air in front of the bb forward, giving the bb less resistance from the air it has to push forward because there is very little left. It won't have to suck in air behind the bb aswell because there is a space between the bb and the barrel (this space should be 0.08).
You should check what size your bb's are, just because it says 6 mm doesn't mean it's 6 mm.
Most companies make bb's that are 5.95-5.97mm. So a 5.95 bb would need a 6.03 barrel to get the best performance. A 5.97 bb would need a 6.05 barrel etc.
I read this somewhere but can't remember where, if there is someone who knows what I'm talking about but can explain it better, please post it to make life easier
Anyway, hope this helps.