I just had my second venom replaced in the last 4 years due to it deciding to be finicky about working. I told Vortex, in a polite but honest manner, that I don't have any confidence in the venom after failure number two. They sent me a Defender-CCW.
Originally I bought two venoms, and still have a working one on the other gun. Can't remember if this second replacement is for one of those two originals or the first replacement.
I know this post doesn't compare it to the Viper. But... I guess I would stay away from the Venom. They work great when they work, but that's not a sure thing in my experience.
