I read somewhere that the best barrel length (for maximum power, accuracy will be the same) for a vsr-10 cylinder is 500-510mm, assuming you have good compression. So, that 554mm barrel won't give you much of a power advantage. Accuracy will be the same, if not slightly worse because the piston will hit the cylinder head before the BB will exit the barrel.. i guess you could get a bore-up kit with that 554mm in order to maximize power efficiency with heavier springs/bb's, but even then there's only a small advantage in fps. And with fps limits, why spend the money? I'd rather save the money for far more important upgrades.