thanks for the comments guys.
the carriage is 2mm (80thou) card cut to shape and then .5 X .5mm (20thou X 20 thou) strip was glued around the edges. The round rods through it were hollow on the real gun but I have used solid rod for strength. The round weld marks at the ends of these were punched out of 10thou card with a 4mm then a 3mm punch, glued in place and covered with glue. After a few moments it was marked with the back of a scalpel blade.
When finished I MAY do a jeep to go with it but I have not made up my mind yet as I cannot get an ordinary jeep kit here at the moment.