Swifty52: Thank you for that informed update.
I am "patiently" waiting for my Ruger rail/base for my MK-IV to get here.
In my travels I am seeing a few MK-IV's in shops and chain stores this past week.
Prices vary a bit (from store to store on similar models) on the three MK-IV models I am aware of and have seen.
Hold into the wind
VarmintGuy