[quote=Ellri]
We'd suggest an era before crossbows become all that common[/quote]
Then we'd be going back way before the 11th century. The medieval crossbow as we know it was in use in Europe from the 11th to 16th centuries. Earlier forms went back as far as the Ancient Greeks, though these were heavier artillery-type weapons. Crossbows almost replaced traditional bows in many European armies around the 12th century, although its disadvantages compared to the longbow were realized decades later.