Got mine from BAR, I tried a T50 and Sightron but decided on the T50s due to witnessing the shift with the heat. To be honest it was a cash buy that I had the money for either, best £600 I've saved in years...
The T50s is not as optically clear as the Sightron but then it is more than half the price, it is however much less affected by heat. Mine moves when the scope goes above 26c and then only to the edge of the number stickers, unlike the sightron I tried. I also tried a couple of big N's, so far it has performed faultlessly through the spring and Summer, the gaps are big enough on the wheel to clearly mark in 2.5yd increments. I've got 8 to 20 in 1yds and then switch to 2.5yds, it is possible to then know when you're between the lines eg 52.5 and 55.
Hope this helps