The current Viper is suspected to be the 2011 version if they sell to Inokatsu.
The bolt carrier and bolt are completely redesign, Bolt catch grabs 1" further back other WA style other carrier are (like KJ) Bolt Catch is mounted on the left side like firearms, the first in WA system. In addition, it also comes with their own special FPS adjuster (NPAS)
Viper runs best on WA standard, not Pro-Win, they tend to have full auto issue.
For more info, see gasgun.info