A little bit about crossbows

So a while back on some forum thread or other, I incautiously babbled a little about medieval crossbows and archery, and my limited experience of same.  Strangely enough, Robin then asked me* if I'd consider guest-blogging a bit about archery, and I said yes, with a couple of caveats.  The first caveat is, I am a terrible archer.  I'm not just being modest—I don't have great vision to begin with, and astigmatism to boot, and when I shoot on a range there is a...