Esteemed member DPowell334@aol.com contributes:
Davis' brigade did quite well initially on July 1st, driving back the initial union line and swinging over to take the Iron Brigade in the flank. However, it was almost certainly Davis' inexperience that allowed his brigade to slip out of his control, get penned up in the RR cut, and lose a substantial number of men there. Had he been more alert to his flank Davis might well have retained a regiment to face east towards Seminary Ridge and protect that line from the rallying Union force of Cutler's Brigade, which was far from out of action.
Other than that, however, Davis did no more poorly than most on the field. The brigade did as well as anyone could have in the Big Charge, for example.
Heth is also somewhat to blame for Davis' problems. Heth committed the two lead brigades to the advance with no support, expecting only fragile resistance. He got his face slapped hard for that over-confidence, and lost a lot of men fairly needlessly. Ideally, Brockenbrough and Pettigrew should have formed the support line, and followed up that initial success.