Still cogitatin' over my pillbox, but I don't think the day has been totally wasted.
I got hold of 6 metres of wire off ebay (32SWG - about 0.27mm diameter) as I wasn't happy with the stuff I'd managed to strip from electrical cable and I've ended up with about 15" (about 380mm) of four-strand barbed wire.
I used a piece of plastic tubing about 15mm dia and a solid rod about 7mm diameter. They should both be the same length and there should be a reasonable difference between the diameters.
Wind a length of wire clockwise along the tube as tightly as you can keeping the spaces about 1/4". Fix both ends with tape and take another piece of wire and wrap it over the first piece - this time though, wrap it anti-clockwise. Remove the tape and gently start to slide the coils off the tube. When you have 4-5 coils free, use a cocktail stick and dab a spot of glue on the wires wherever they touch. This will hold both coils together and create a single, multi-strand coil.
Do exactly the same, using two pieces of wire wound in opposite directions around the smaller rod. Again, gently slide the coils free from the rod and glue wherever they touch.
Slide the larger coils back over the tube, and slide the smaller coils inside the tube. If you gently grab one end of both sets of coils, you should be able to slide the tube away and leave one set of coils inside the other.
I ended up with this ....
View attachment 76120
View attachment 76121
.... a single coil of 4-strand barbed wire.
Gern