At the end of the 17th century, a flaw within the design of matchlock muskets became more apparent. Since the matchlock musket used a slow burning piece of twine known as a slow match, the twine sometimes would accidentally set fire to the gunpowder reservoir in the musket prematurely setting off all of the gunpowder and bringing serious injury and death to the operator. During this time, matchlock muskets began to be replaced by lighter and cheaper infantry fusils with flintlocks, weighing 5 kg with a caliber of 17.5 mm, first in France and then in other countries. In many countries, the new fusils retained the name "musket". Both muskets and fusils were smoothbore, which lessened their accuracy and range, but made for faster loading, lesser amount of bore fouling and more robust, less complicated firearms.