I believe he did not serve in the 91st. See my note under 'After the war' below.
He was buried in the Evangelical Cemetery near New Paris, in Napier Township, Bedford County, Pennsylvania (1). He is presumably the John M Hiner who was buried in the New Paris Community Cemetery, New Paris, Bedford County, Pennsylvania (2). If so, he served in company F of the 99th Pennsylvania Volunteers (2).
not in Bates, Samuel Penniman. History of Pennsylvania volunteers, 1861-5. Harrisburg: B. Singerly, state printer, 1869-71. 5 volumes. 'Ninety-first regiment', volume 3, pages 186-233.
1 message, from David and Carol Eddleman, 9 November 2002, on PABEDFOR list at <sites.rootsweb.com>, transcribing burial list from the Bedford Inquirer, 22 May 1908 (John Hiner)
2 Find a grave, memorial 26680729, created by Kat, 8 May 2008, accessed 15 January 2011 (John M Hiner)