Hi John,
The Rhino .25 tin I still have is the last remaining tin from the batch I bought ex. gun shop closure many years ago, most of which you purchased from me, so not being very mobile at present, and out of interest, I will weigh some of the contents to see what differences in weight I find.
I also have a few tins of Webley Mosquito .25 - 6.35mm and Bisley Pest Control .25 - 6.35mm, neither of which state any weight on the tins, so I may weigh a few of them as well.