I have an artical based on test notes by O'Connor or that guy that did all the pistol shooting .
Any way , they took an '03a3 30-06 with a 30" bbl shot like 100 rounds of a single lot of mil. ball for a net average then cut and crowned the bbl 1" and repeated the test really big losses started under 18" like 150-250-an in. but the drop from 30" to to 22"was only about 200 fps . The losses from 26" - 22" were less than 50fps as I recall and there was an increase at 1 interval in those lengths .Keep in mind that this was a GI rifle and milatary ball ammoand shot over about a month and 100 rounds per length . The losses from 22-24 I'd bet 50 or less .