Why would you ever need such a long barrel?
I don't understand people that hide barrels in silencers. A quality 363mm barrel is JUST as accurate as a quality 650mm barrel, might as well use the sound dampening silencer as another advantage.
Case and point, my VSR-10 is just as accurate as Amos' and it was almost half as long.
Case and second point, my HFC beretta outranged and was more accurate than any stock AEG, and it had a 6.08 barrel less than 80mm in length.
COMPRESSION, its all about COMPRESSION!
Your actually getting less accuracy in a barrel thats at the maximum length for your cylinder, than a barrel thats at the minimum length of the cylinder.
So say full cylinder can take a barrel 470-590mm, then you'll be better off using a 470mm barrel