Neil,
The page below gives a weight of 5 tons>
http://www.mapleleafup.org/vehicles/carriers/index.html
Wikipaedia gives the weight as 3.75 tonnes.
This site gives the weight as 4.31 tonnes.
http://www.stenboye.dk/carrier/
And this one gives a weight of 4 to 4.5 tons.
http://www.angelfire.com/art/enchanter/bren.html
There again, there are those on the Forum who will leap to your assistance with utmost alacrity
Paul.