Adam, I'm guessing the 20 was a little loose. I ordered a 19 and a 20. The 19 would go on but it was real tight. I wasn't sure if I would have problems in the field trying to open it. Went with the 20, fits snug and I have not had any problems.
As for the Mueller scope,I have it mounted on a AR. I love the sport dot feature. Have not shot much over 100 yards with it. I'm very pleased with it for the price. Not as clear and crisp as a few of my Luepold or Nikon scopes but at a third of the price you can't go wrong. /ubbthreads/images/graemlins/grinning-smiley-003.gif How do you like yours?