Yes, I remember that on my first read I had to go over this passage a couple of times to make certain that it did indeed indicate what I thought it did. But it fits with Brandon's character, to keep the incident so subtle and low-key.

All right, then--I imagine it must have been pistols, because if it had been swords, somebody would almost certainly have been wounded. If both fired together, then they must have both missed; I don't know a lot about period firearms but I've read that they were notoriously inaccurate. If they didn't fire together, then I'd imagine Willoughby would have fired first (as the challenged party) and missed. Now comes the sticky part: what did Brandon do? Did he miss as well? Hard to imagine that a military man would be a bad shot, though again, the firearm itself might be at fault. Or did Brandon deliberately miss--fire into the air and spare Willoughby's life? It would be like him to do so (after giving a thorough scare first). Honour would be satisfied, and I can see him staying his hand because killing Willoughby would make Marianne unhappy.