The way you are doing it on your build is just fine. I will add some pictures of the ways I know.
There is the "cut splice" way. which is a bit difficult to do for a model.
Wrap around the cascabel like The way you have done on your build log.
The next one only works if there is a ring on the gun.
There is another way with a four-strand rope but I don't have any pictures. I've also seen some breach ropes that run through the carriage itself and not even touching the gun.