I think 6 "Thou" would be a little fine. It works out at 0.15mm dia, if you X by 16 it comes out at 2.4mm real life size.
I've never actually measured any Barbed wire, but I think this is too fine.
I'd say that somthing like 4mm wire would be "In the Ball Park". Divide this by 16 and it works out at 0.25mm.
As for making ... I made some for a 1:35th WWI tank, it's a little overscale, but the end result was quite pleasing.
Small strip of wood (something like 2x1") drive a small pin in at each end.
Now twist two strands of wire together to make the initial wire.
Then (painstakingly slowly) make the individual "knots" and trim the ends to the desired length.
Once this is painted/weathered it looks great... Well, I was happy with the results I got, see following...