Fergus, You hit the nail on the head. I test at 100 because with the flags i can see what is going on and i shoot in the same condition. After i develop a good load i will test the load under different conditions head and tail winds left and right to see how the combination reacts to the condition change. Right now i have the best combination i ever had, so i now check the quality of the barrels i will use for the upcoming year. This is simple, have your point of impact below your point of aim and hold the same point of aim for 180 wind conditions of about 10mph. and see if get a big hole or a weather report. if you get a hole take it off and mark it for the national and screw on an other one and test it, the smaller the hole the better. If they string them out it may be so wind sensitive it isn't worth messing with a small amount of stringing maybe average, you will get the picture after you try it a few times and with different barrels. Remember when you have a hummer don't waste it and the wind will be your friend…… jim