George, another belated thanks for your help. I've had a chance to do a little more research and I THINK I have a better handle on my Great Grandfather's service. I now believe that he's the one you noted in the previous post, Co E of the 7th BATTALION Miss. Infantry. I have seen the service records for this John W. Ellis at the Miss. Dept. of Archives and History and the places and dates seem to jive. Some other family historians are telling me that he served in multiple companies, but at THIS point, I don't see that.
In addition, after doing some digging on Ancestry.com, I found another John W. Ellis in the 1850 Census that would have been the same age as my g-grandfather, AND he resided in Monroe County, where Co. G of the 41st was mustered. Still don't know why records show that many men in that unit enlisted in Meridian, though.
A story that I've heard from more than one family source tells of my g-grandfather being shot through the mouth (from the side, I presume) knocking out several teeth during battle at Murfreesboro. I'd had trouble reconciling that with the record, as it seemed unlikely that he could have been at the Battle of Stone's River with the 7th b'n. Looking more closely at the unit's record, I see that they DID see action around Murfreesboro later in the war, but not during that famous battle.
One question remains, though. Records show him in Co E, but the marker someone put on his grave says Co B and I've been told that a medal was found at his old home place that says Co. B 7th Battalion.