The FX Impact Superior Smooth Twist X Barrel Kit features rifling throughout the entirety of the barrel instead of the last few inches. This design is unlike any other barrel made. The rifling is pressed from the outside resulting in a smooth surface that has never been achieved inside a barrel before. Helps reduce resistance in pellet travel which in turn reduces lead deposits and makes cleaning easier. There has been talk of an improvement in overall accuracy and more leeway in tuning the rifle while maintaining accuracy. The 700 mm version gives the pellet a longer runway to pick up speed which results in less air needed to achieve the same velocity as the standard 600 mm version would. Longer barrels generally improve all aspects of the shooting experience but sacrifice portability.
FX claims a 10% increase in muzzle energy over the 600 mm version.