Ben, I built a sheetz rifle ( late Virginia ) with a 36cal. 7/8 x 42 barrel and it was heavy. I didn't weight it ,but it had to be close to 10 lb. I was like you and already had the barrel so I went ahead and used it, boy that was the wrong thing to do. I wish now I'd takin a grinder to it and thinned her out some. You wouldn't want to go much shorter than 40 in on a fullstock, maybe 36 or 37 on a halfstock that's just my opinion. You didn't really say what kind of southern rifle, I think everyone assumed you meant fullstock/ flint. If I were you I'd be ordering an A weight / 42 in for a fullstock and put that one you have up FOR SALE , Good luck and thank you for your service to our country