Copson's served from Aug. 15, 1861 to July 24, 1865. Assuming he was present throughout then he was at the battle of Pea Ridge, Ark. (March 6-8, 1862), Perryville, Ky. (Oct. 8, 1862), Stone River, Tenn. ( Dec 30, 1862-Jan 3, 1863), Siege of and battles about Chattanooga, Tenn. (Sept 22-Nov 27, 1863). Atlanta, Ga. Campaign (May 1-Sept 8, 1864), March to the sea/Savannah, Ga. campaign (Nov. 15-Dec. 10, 1864) and Campaign of the Carolinas (January-April, 1865). The regiment lost 14 Officers and 139 enlisted men killed or died of wounds and 190 enlisted men died of disease or other non-battle causes=343.
Source: Dyer's Compendium of the War of the Rebellion; Report of the Adjutant General of the State of Indiana

I could not find a regimental history of the 22nd Ind. Infantry, written either by veterans of the regiment or by a more recent author. There are histories of the Army of the Cumberland that would give you a general idea of Copson's service through the Atlanta campaign.

I found battle reports written by the different regimental commanders if you are interested.

The National Soldiers Home in Indiana is at Marion which helps explain why Copson is buried in the National Cemetery at Marion.

The home was opened in 1888 but I can't find year that Copson became a resident. Records of soldiers who resided at the various homes are at the National Archieves

Ft. Omaha or Omaha Barracks dates from 1868.

Both the Marion home and Ft. Omaha have internet sites