The V3 is better reinforced than the V2. It has extra metal in it where the V2 doesn't. You get less of a problem with cracking and hair-line fractures.Peyote said:woogie I believe the biggest difference is that the V3 is slimmer than the V2 which means its used in AEGs such as the G36/AK/SIG. People also say that the V3 is able to handle more pressure and stronger springs but that's all up for debate.
To add onto this (Although none of this matters for the fusion engine) the V3 has the motor attached to the gearbox as well.
I kind of wish they'd make a V2 with the same reinforcements as a V3.