Hi drewlear,
My grandfather was in the Royal Field Artillery too. The Gnr is most probably Gunner abbreviated, have you tried looking on the National Archives for more info. I believe thats where I found the online details for my grandfather, even down to his eye colour, height, whether he had any scars in his case he had tattoos. It also gave details of his wife and children and their dates of birth and of course marriage date of him to our great grandmother.
Wish you luck on that.
Gossip64
