Ben...
I have a nice article by James Groves , on the Gettysburg,Devils Den Sniper. Mr. Groves pretty well proves that the photograph made at the devils den was a fake, and the actual sniper rifle used by him is in the Gettysburg museum. He includes a picture of the rifle.
Try this ,I hope it works for you.. http://www.jamesgroves.com/henry/hcp3.htm