I'm not sure if you found this in your Googling, but there is a pretty comprehensive history of the Stirlingshire Rifle Volunteers starting on page number 320 of the document linked below. It starts out by stating that the 1st Administrative Battalion, Stirlingshire Rifle Volunteers, with headquarters at Stirling, was formed on 9 June 1860, and then goes on to list the individual companies and their dates of formation, including the 1st Stirling Corps formed at Stirling on 14 October 1859, the battalion eventually reaching a total of 12 companies.
In March 1880 the battalion was consolidated as the 1st Stirlingshire Rifle Volunteers, being reduced to 10 companies identified by letters rather than numbers with the 1st Stirling Corps becoming A company. With the Childers reforms of 1881, the 1st Stirlingshire Rifle Volunteers became the 4th (Stirlingshire) Volunteer Battalion of the Argyll and Sutherland Highlanders.
Given his assumed birth year, your ancestor would have been in his early 30's when the Stirlingshire Rifle Volunteers formed, so it would certainly seem to fit.
https://electricscotland.com/history/scotreg/recordsofscottis00grierich.pdf
