Originally Posted by MaciekA
First, (as others have mentioned and you'll surely hear about on Airsoft Mechanics), the effects of barrel length are extremely interesting. Once volume has correctly been matched to the cylinder and correctly accounted for relative to the strength of the spring, is there any effect whatsoever in lengthening the barrel beyond the exact match implied by the (port-adjusted) volume of the cylinder?
Like I've said before, there's a maximum range and accuracy that can be achieved with a given weight of BB
Once you've topped out the performance capability of the BB, nothing you do to the gun is ever going to make that BB fly further or straighter.
So with any BB your optimal relative velocity is around 320-350fps, any faster and it destabilizes too quickly, any slower and you're just not getting the most out of it.
Once you hammer out barrel, volume, and compression requirements, the only thing left is barrel length. It's just a question of at what point does the BB stabilize itself within the barrel. For GBBRs and pistols, that's about 80mm or so, much more difficult to tweak with GBBRs since longer barrels tend to raise fps, which requires heavier ammo, which in turn raises the muzzle velocity even more.
AEG's tend to stabilize perfectly around the 420mm mark. Any barrel beyond the point of stabilizing is just useless metal. It's allowing more time for the BB to be DE-stabilized by potential fouling in that barrel.
Two VSR-10s built exactly the same internally, one with a 650mm barrel and one with a 420mm barrel, both shooting .3s, or one at 380 and one at 470, or 470 with .36s vs 440 with .3s, doesn't matter what combo we use, the 420mm barrel was never bested by the 650mm in terms of accuracy.
In fact, the 650mm barrel had worse accuracy when using .3s at 470fps
The idea that longer barrels increase accuracy in airsoft was carried over from real steel, but the physics of the two are completely different.