All I seem able to do is confirm what you have.

U.S. Civil War Soldiers, 1861-1865
about Samuel C. Williamson
Name: Samuel C. Williamson
Side: Confederate
Regiment State/Origin: Georgia
Regiment Name: 48 Georgia Infantry
Regiment Name Expanded: 48th Regiment, Georgia Infantry
Company: H
Rank In: Sergeant
Rank In Expanded: Sergeant
Rank Out: Sergeant
Rank Out Expanded: Sergeant
Film Number: M226 roll 65

Would this be his son?

1900 United States Federal Census
about Samuel C Williamson
Name: Samuel C Williamson
Home in 1900: Militia District 50, Emanuel, Georgia
Age: 40
Estimated birth year: abt 1860
Birthplace: Georgia
Relationship to head-of-house: Head
Spouse's name: Sinel
Race: White
Occupation: Farmer
Neighbors: View others on page
Household Members: Name Age
Samuel C Williamson 40
Sinel Williamson 29
Anderson Williamson 12
Elder Williamson 10
Oley Williamson 8
Cannie Williamson 6

There is another Williamson listed as a neighbor named Varney Williamson with wife, Venik(?), sons Sidney and Leroy and daughters Bula and Felma.

I've checked the listings for Richmond and area but don't find him listed. I also checked the two vol set by Mark Hughs but did not find him listed. It is possible that he was buried in a mass grave, known only to God. I will check my 18 volume set this weekend and see what I can find.

Samuel C. Williamson
Regiment Name 48th Georgia Infantry
Side Confederate
Company H
Soldier's Rank_In Sergeant
Soldier's Rank_Out Sergeant
Film Number M226 roll 65

48th Regiment, Georgia Infantry

48th Infantry Regiment completed its organization at Macon, Georgia, during the winter of 1861-1862. Its companies were recruited in the counties of Burke, Glascock, Warren, Richmond, Jefferson, Emanuel, and Harris. Ordered to Virginia, the 48th was brigaded under Generals Ripley, A.R. Wright, and Sorrel. It served on many battlefields of the Army of Northern Virginia from the Seven Days' Battles to Cold Harbor, then was involved in the long Petersburg siege south of the James River and the Appomattox Campaign. This regiment reported 33 casualties at Mechanicsville, 44 at Malvern Hill, 61 at Second Manassas, and 72 at Chancellorsville. It lost more than fifty-five percent of the 395 at Gettysburg, and there were 32 disabled at Manassas Gap. On April 9, 1865, it surrendered 13 officers and 193 men. Colonels William Gibson and Matthew R. Hall, Lieutenant Colonel Reuben W. Carswell, and Major John R. Whitehead were in command.

Also in this unit was:

Schley H. Williamson
Regiment Name 48th Georgia Infantry
Side Confederate
Company H
Soldier's Rank_In Corporal
Soldier's Rank_Out Private
Film Number M226 roll 65

Co H = Emanuel Guards, also McLeod Volunteers