Leapers has made a very short tubed scope for years and I have put a lot of them on my carbines and other peoples guns. I tried them because the only other available short tube scopes were the Weaver K series and the field of view on them is not to good. I always bought fixed power scopes and maybe that is why I had good luck with them. Over the years I found that when people have trouble with cheap scopes, it is usually with a scope that has adjustable power.
A few years ago I mounted a short 4x32 Leapers on an old single shot 12 gauge so I could use it for a slug gun. I ran a lot of boxes of slugs through it both hunting and at the range and it still works fine. Try that with some name brand rifle scopes and it would shake them apart. You better believe that a 18" barrel single shot 12 gauge really kicks.