I can't shed light on the Reilly question, other than to say Reilly was amongst those building the first breech-loaders (with Lang and Blanch) before the Birmingham crowd got involved. In any case, output was small at that point, for everyone concerned.

On the matter of Reuben Hambling, he was a gunmaker, of that I have no doubt. Born in 1833 in Blackawton, Devon, he apprenticed under his father, William Bartlett Hambling. He married in London in 1858, had a daughter there in 1861, and was listed in the 1861 census. He was most likely working as a journeyman for a London gunmaker, name unknown. He was in Manchester from 1865-1869, with his own shop at 27 New Bailey Street, Salford. He may have occupied another address for a time, on Bexley Street. He then moved to High Wycombe northwest of London around 1872 and lived for a time in Brighton (1874-1875), possibly working with his brother William, another gunmaker. From at least 1884-1885 he lived in Paddington, London, on Ashmore Rd. This may have been the time when he was employed by Reilly. After this, he moved to Ashford in Kent, with a business at 41 New Street. He lived at number 39. According to the 1891 census his son, Roger, was apprenticed to him. Reuben Hambling died on 12 December 1891. His son continued the business until 1894.

I realize there are a lot of gaps and maybes when trying to pin down individuals in Victorian Britain, more so when dealing with working-class men and not royalty or celebrities. But between census data, newspaper accounts, business records, and genealogies, at least a fuzzy picture emerges. Oh, and there are guns. Here is a bar-in-wood game gun signed Reuben Hambling:

[Linked Image from i.imgur.com]