Your great, great grandfather fought in one of the most storied Confederate brigades of the war -- Gregg's/McGowan's South Carolina brigade.
The web pages Jim has advised you of are good ones. I believe the online version of the Caldwell book The History of a Brigade of South Carolinians Known First As "GREGG'S" And Subsequently As "McGOWAN'S BRIGADE" is not quite complete to the point of having the entire book online, but most of it is. Caldwell's book is one of the most comprehensive and detailed accounts of any brigade in the Civil War, and I believe is available in reprint form from some online booksellers. You could also get a copy via interlibrary loan.
Two other good books specifically on the 14th S.C. of this brigade are "A Colonel At Gettysburg and Spotsylvania" by Varina Davis Brown and "Dear Bet -- The Carter Letters, 1861-1863" edited by Bessie Mell Lane.
Two other websites will interest you. One is an online version of the book Fox's Regimental Losses. Below is a link to one page of the book. If you scroll about 3/4 of the way down the page, you'll come to a table from Caldwell's book that summarizes the very high number of casualties suffered by Gregg's/McGowan's Brigade, broken down by regiment, and of course including the 14th S.C.
Another is a link to a website of a former firearms auction by a large New England auction house which handled the sale of Wiley Sword's firearms collection several years ago. Below is the link. Scroll down to near the bottom of the page to Item # 22. It features a photograph of an Enfield rifle musket carried my a member of Co. I of the 14th South Carolina Infantry (James Marshall Hill) and describes the weapon in considerable detail.
I have done a fair amount of research on this regiment and brigade, and would be happy to share more with you if you are interested, including a postwar reunion photograph of some members of the 14th S.C. Infantry. Just write me back and my e-mail below if you are interested in discussing this further.
By the way, do you happen to have a photograph of your g.g. grandfather? If so, I would be interested in seeing it!