I've not seen this photo before. It was actually used at a website for the Civil War. But those depicted actually have the Krag-Jorgensen rifle. It was titled "falling in line" at Chickamauga, Ga. Of course the picture had to be taken years after the Civil War. It appears that a few are looking at their rifles for the first time. Maybe they just got handed out? They seem to be focused on the sling.