I wish I could say this was the first time I've run in to this issue. Sometimes it's avoidable as manufacturers are either accurate in their measurements or they include an actual length in the fine print. I ran the numbers and a 10.5" barrel with a KX5 should have protruded around 1/4" from the end of a 13" rail. That only works if the 13" rail is 13". Time and money wasted again. First world problems I know but frustrating nonetheless.