Your impression is correct. The 13th North Carolina Infantry were issued jeancloth NC shell jackets in April and June 1862 after initially being issued NC sack coats the previous October and December. These type jackets were issued regularly to this regiment up until the end of the war. From mid 1864 onwards many NC jackets were manufactured from imported English blue/gray kersey. There is a surviving uniform comprising blue/gray shell jacket and royal blue pants issued to Alfred May of the 61st NC Infantry. The jacket is thought to be of NC manufacture, initially with the usual 6 button front, but with 5 extra buttonholes added after issue. The 13th were also issued large quantities of caps right up until the end of the war.