Jim, I'm using a new style T6 with the locking A.O. ring.

  At 100 yds, I can set the parallax and tighten the lock ring with no apparent change in parallax.

   At 200, I need to go past where the parallax is eliminated, work back in, and tighten the lock ring when there is just the tiniest amount of parallax. Tightening the lock ring there will shift the lens alignment just enough to get it parallax free.

    At 300,  I see the same effect as at 200, only more pronounced.

    The new Sightron 6HBR scopes have the lock ring at the very front of the A.O., and I think this is a better way to do it as you are tightening the A.O. against the threads rather than pushing it away as the T6's do....kind of like making an 'up' adjustment on the elevation knob by going past where you want to be and then coming back down to load the threads and tension the adjustments a bit better.

    I also have heard that the Burris scopes with the crosshairs are having some parallax problems as the crosshairs are on two different lens that are butted against each other, thereby making them on two different focal planes and making it difficult to get decent parallax adjustments. I understand that the .375 dot models have all this on one lens and have no such problems.

   'Ya know...if some mfg. ever decides to give us 6X shooters what we want and will gladly pay for, he will be able to make enough $ to vacation to exotic locations of his choosing, or at least get as far as Madrid, Iowa or Westbrook, Minnesota....probably would run out of gas $ before he got to South Dakota, though! HeeHeeHee!  -Al