I have two of the 4-16x40's bought from Walmart. One is on an AR and one on mt Rem. model 5 22lr.
Actually had to exchange one, but the two I have are OK now.
The optics are fairly bright up to 12x, but beyond that they get pretty bad with eye placement being very critical and the contrast and sharpness going downhill very fast at higher magnifications than 12. Buy it knowing that it is usable up to 12x, but beyond that it is a crap shoot. Both of mine above 12x are really bad.
The lit reticle (red and green) is too bright in dim conditions (even at the lowest settings). The highest setting is pretty good in daylight when shooting at black targets like the center of bulleyes.
Overall for $70 scopes, not too bad. Nothing as nice as even $200 or $300 scope though, so don't expect that kind of performance.
My son's inexpensive $200 Burris Fullfield II 3-9x40 scope kit (packaged with cheap $40 rimfire 3-9x32) is much better in all respects.