Long Branch started their sniper program in 1943, so I think unlikely that if yours is a 1942 that it is what you think. In 1943, LB produced 73 snipers, which were from various serial number ranges. They were mounted with an REL Mk1 No.32 scope. Mine is a matching rifle/scope setup. These were the preproduction run, as "official" production began in 1944. As you stated, they did have problems with the hardened steel, (makes we wonder about the H & H method, what was different?), so they did start working them in blocks, most often found in 71L range and 84L. Many of the early rifles were not stamped with the "T". If the rifle saw Britishservice, it is presumed that the British armorers "made it right" and stamped the "T". Cleve Law has a book you need, if you are interested in more about Canadian
snipers. I've not heard about a "T" stamp on the underside of a receiver. Is it the characteristic "T" ? They made about 1,250 snipers, finishing up the program in 1946. I need a Canadian -15 box, if you can find me one! Post some pictures. hth
PS: Out of Nowhere by Martin Pegler (sp?) has a few pages of good information on the Canadian sniper program.