Hi Paul, There are no Harris's with the initial G in the 14th or 15th Bts, but there are 2 original voluntees in the 16th Bt RWR, the first is: Pte 907 G.M Harris, but the most likely one for you is: Pte 341 G. Harris, KIA 16/04/1917, he is buried at La Chaudier Militry Cemetry.
Chucka