In looking for lesser known Military resources in Canada I came across this website: Vancouver Gunners. The site explains that it covers the Artillery on the mainland of B.C. and specifically the 15th Field Regiment.
The site has a Nominal Roll that you can look through for your ancestor. Another great resource on the page is their Yearbook, this is slightly different than a typical yearbook. It explains on their webpage it is a “collection of memories over the history of the Regiment”. The yearbook starts in 1910 and goes all the way to present day and has biographies for the soldiers and there are also photos for some.
Good luck with your Military research!