I recently decided to download the quarter bore for permanent foxing / thermal use, Always used to shoot .223 fast twist 69 grain in the past, but no longer having that set up & having picked up some very heavily populated fox ground, I sourced a box of 75 grain V Max .257 bullets, loaded them over 43 grains of N140 in new Nosler brass & tested these earlier this last week ......... sound of report gone from the 100 / 117 grain boomers down to an acceptable mimic of the old .223 ... accuracy over a 200 yard zero is one hole for three rounds rapid, then a crosswind test of 90 degree left to right with a pretty stiff wind, gave a poi shift from the bullseye mark 6 " to the right But still at same elevation as into wind shots, very satisfying strike sounds on the four fox taken so far, my chrony is out on loan to a friend locally, but I am guessing it's running around a gentle 2800 / 2900. 
