I dunno Al. A 308 drops about 4in at 200yds and an HMR17 drops 8in. (100yd zero) I'd take a shot at 200yds with an HMR17 and feel more confident about it than a 308 at 300 (15in drop). Well... except for my present situation that is.
I'll take your advice and try again at 25yd increments and see if I can tell where things fall apart. Thanks. But I'm still concerned about why I'm such a lousy shot compared to my first few days with the 17.