I was recently reading an old artical that used a '06 that started at 30 inches and was cut back an inch at a time using mil match ammo of one lot .I don't recall the volumes of ammo but but it was like 100 rounds per length . The last cut was at 8" . The velocity drops were not what you would expect at all . The drops were 10-20 fps per in down to 26 inches at 24 or 25 velocity went up then down again . From 26" to 22" the drops were flat . At 18 big drops showed up at 12" the 2850 of the 30" bbl was about 1200 at 18 the rifle was still over 2550 . I think the tests were done by Akley but I can't find the artical .