It is the spped of bb, while its leaving the innerbarrel of replica. This speed is measured in FPS (Feet Per Second).
1 FPS = 0,3 m/s
1 J = 99 m/s
1 J = 326,7 FPS
Type of fire
Magazine capacity [pcs]
Hop-Up system is used for overclocking bb during the shot (putting it in rotation), through which, it extends its flight path. Acting laws of physics make that bb lift up, while the gravitational force take it down. Appropriate adjustment of Hop-Up, will compensate for these two factors, which result in long and straight flight for longer distance and be greater focus shot (to improve accuracy).
Blow back is a simulation system of the cocking lever - it imitates the
work of it as the equivalent sharp. This system raises the realism and
adds a lot more experience during shooting.
For this price, the KCB12AHN (Sigma) is an excellent replica and fun to shoot with. It feels heavy and sturdy, there's a little rattle on the metal slide, but overall it feels solid. The blowback is hard and the it gives a metal "klack" sound. The fps is high, definitely not recommended for CQB (close quarter battle).
I can imagine that people might find this replica a kind of boring looking, because of the smooth, structureless plastic body design and smooth grip, but that is just a matter of taste. The replica feels good to hold in your hand. The only disadvantage would be the slide lock, which is made of a thin metal piece. It would have been better if the lock was made of a thicker piece of metal.