The K-6 is an excellent, tough scope! I had a Weaver K-2.5 and was able to kill woodchucks at ranges beyond 400 yards, provided someone with binoculars spotted for me and the chuck's side-hill mound was visible in the scope.
The power of a scope is not a relevant measure of the increase in accuracy afforded over that of iron sights. One needs to consider the fact that both target and reticle are on the same plane and brightness is enhanced. There is also no change in sighting accuracy when the sun is at different places with regard to line of sight, as there is with an exposed front sight and rear notch.
Also, a 6X scope with a target compatible with reticle size, can be nearly equal in accuracy to a 20X scope, according to tests done many years ago with three scopes and iron sights mounted on the same bar.