I was in EW yesterday messing with the SdKfz251.
We had captured the v base next to the enemy HQ on the Baltic map.
A freindly in a Panzer spawned with me to HQ. He was on train kill detail to stop the re-supply of the HQ.
I ran sorties with 4 box supplies and 6 rockets.
After spending 2 or 3 rockets to find the range to HQ I dropped the 4 boxes, fired the remains of the loadout, re-supped myself ect...
The next sortie all rockets hit HQ...30 rockets. I did this for another 3 sorties. HQ goes BOOM!
I think I did 5 soties in total 6 rockets + 4 re-supps = 30 x 5 = 150 rockets (less 2 or 3 to range)
I read that each rocket is = 280lbs of HE
280 x 6 = 1680lbs
+ 4 supps 6720lbs
total ords p/sortie 8400lbs

I had great fun in that little half track although I can't find information on it's historical cargo carrying capacity.
I found the vehicle weight of around 7.8 tonnes. Add the AH load out and allow for the driver gunners etc..
brings a gross weight of around 11.8 tonnes
I will be using the 251 a lot more. Ranging can be tricky but well worth the time.