Andy,
  How many yards can you get at your place? I borrowed the old game wardens laser radar gun which not only shoots M.P.H., but shoots and reads out distance. I have 1678 feet, over 500 yards. Mostly we shoot off the shelf guns as you put it, but they work okay for my abilities. My son bought a bolt action Vulcan Arms  50BMG .....yikes! ....and very good accuracy too! Ammo is pricey tho' and so is the initial reloading setup.
  (I also like the winchester101,in 20 gauge)
                      Cal