The Evanix Viper is a semi-automatic PCP air pistol.
You cock the mechanism by pulling back the slide above the gun (and pushing it forward again).  When firing, the gun loads the next shot in a fraction of a second.
On the slide and frame of the pistol are 22mm picatinny rails for mounting optics such as a red-dot or pistol scope.
 
The operation of the gun is quite simple with a safety catch on the left (operated with the thumb) and a small window on the right to see if the gun is cocked.
For adjustments to the hammer spring, the adjustment screw on the back of the Viper can be used.
 
With 21 to 27 joules, this is a fairly powerful PCP air gun that can also be quite loud.
Fortunately, there is 1/2unf thread on the barrel with which a silencer can be mounted.
 
The primary compressed air reservoir is located under the barrel and the secondary compressed air reservoir is located around the barrel (as a barrel shroud).
These reservoirs can be filled up to 250 bar using the Foster connection at the bottom of the Evanix Viper.
The average number of shots per caliber (after a full fill) is as follows:
 • 5.5mm / .22: 14 shots
 • 6.35mm / .25: 12 shots
 
The spring-loaded rotary magazine reliably feeds ammunition to the semi-automatic system.These magazines have capacity for:
 • 5.5mm / .22: 7 bullets
 • 6.35mm / .25: 6 bullets