It's the same thing going on that seasoned competitors experience with many good quality match barrels, some will shoot a certain load smaller in a specific wind condition......some will shoot smallest in a L>R, some combinations will favor R>L.
A hummer just does it better and may be more indifferent as to wind direction. IIRC as described in TB's book, a good match bbl. will allow the shooter to avoid any hold-off with a 1 hr. change in the flag tails ( 1 hr = the tails @ 60 degrees to ground), a great bbl. = 2 hr. change ( 45 degree) , and a hummer a 3 hr. change ( 30 degree)
A hummer just does it better and may be more indifferent as to wind direction. IIRC as described in TB's book, a good match bbl. will allow the shooter to avoid any hold-off with a 1 hr. change in the flag tails ( 1 hr = the tails @ 60 degrees to ground), a great bbl. = 2 hr. change ( 45 degree) , and a hummer a 3 hr. change ( 30 degree)