Most of the electric airsoft rifles have an adjustable hop-up feature incorporated into the gun itself. There are cheap electric airsoft rifles that do not have this feature, but this does not mean that these type of guns are inferior, they will just not be able to allow the shooter to dial in on their opponent as well.
A hop-up is an adjustment that determines the amount of spin that the bb achieves as it exits the muzzle of the gun. This allows the shooter to determine the speed and trajectory of the ammunition depending on the situation at hand. The majority of electric airsoft rifles will fire the ammunition from the muzzle at a velocity of approximately 300-400 feet per second.
Many metal electric airsoft rifles incorporate a metal, high capacity magazine that will hold from between 250 rounds up to a whopping 600 rounds. This insures that the shooter has a seemingly neverending reserve of ammunition at their disposal. Adjustable sights and optic mounting rails are also great features of many electric airsoft rifles, and some even employ a folding or adjustable buttstock to accomadate just about any sized shooter. This is especially true of the full metal electric airsoft rifles.
Another great feature that some of the electric airsoft rifles offer is a realistic blowback action. These electric blowback airsoft rifles have a slide mechanism that actually moves back and forth making a very lifelike sound, more like a 'clack', and is similar to the actual sound of the real thing. This added detail makes these electric airsoft rifles a real blast to shoot. Behind the slide is where most of the adjustable hop-ups are found. Moving the adjustment backward and forward is what puts the extra spin on the ammunition.