No, shore lines & high water mark is something else.
this was something I read fairly recently, last year or two, and was almost a throwaway comment...
You can shoot in the middle of the carriage way if you don't cause impedance to travellers. 50 foot is about 16 yards or bloody close if you prefer....
2nd FP could be described as adjustable as the "ret adjusts when mag is altered even though it actually should remain proportionate. Probably a case...