Fred, I just looked at this page again and saw your inquiry regarding my g-grandfather Ben F. Jackson's service with the 15th Texas Infantry.
Here is a short synoposis of the "Battle of Sterling's Plantation: This major battle of the Civil War took place within Pointe Coupee Parish, La at the Fordoche Bridge on the Atchafalaya River. After the Union defeat at Sabine Pass earlier in the month, the Union forces sent a 1,000 man detachment, the 2nd Davison, XIII Army Corp, to control the river, and make ready to disembark on the plains and march overland to Texas. The Union army met its match again. The Texas forces began crossing the Atachafalaya River on 28 Sept 1863 with all forces over the river by midnight. On dawn of the 29th the battle was over. Confederate cavalry began skirmishing the Union pickets at Fordoche Bridge before noon and continued for about a half hour. The Texas troops hit the Union forces again, drove them and captured many. Gen. Tom Green and his Texans had defeated this Union force handily with over 575 Union casualties, 454 being of the Union army and 131 other casualties with only 31 CSA casualties reported (others being slaves and other persons within the line of fire of the Union cannons which were later captured by the Texans.
As to your question about "Sharpshooters", it was most often a good shot within a unit that was assigned the duty. The got their name because the "Sharp" rifle was the most accurate of the day. Those early sniper rifles weighed from 14 to 24 pounds so the Sharpshooter didn't run around the battle field.
Today Snipers are in special units and then assigned to field companies. Although they have been used in every war in which we have been engaged they were not organized into a speciality until Vietnam. If you would like to know more about this speciality I recommend you purchase "One Shot One Kill" by Craig Roberts. It's available at Amazon.com. Craig is a good friend of mine who served as a sniper with the Marines in Vietnam. His book is a good read.
If I can answer any other questions you can write directly to me at firstname.lastname@example.org