Jim, there are several accounts of 23rd Illinois soldiers using Henry's during the Fort Gregg fight. Somewhere in my files I have an account w/ photo of a Henry w/ the 23rd Illinois soldier's name inscribed on the rifle stock. The best way to contact me is at anglevalleypress@yahoo.com
Good luck w/ your regimental and be sure to look into Fort Mulligan at Petersburg, WV named after Colonel Mulligan. It was built in the fall of 1863 to help deter Confederate partisan ranger operations in the Upper Branch of Potomac River area. I wrote an article for America's CW magazine about this several years ago called "Between Two Valleys." The fort is still there and quite well preserved.
John Fox