95 FEET TARGET. This is the final video in the Archimedes Heat Ray aka Death Ray. I think it would have been possible. Previous tests had the following flaws.
By adding a mild beNd to the mirror, the light can be concentrated at 100 ft for a 12 inch mirror or larger. This increases each mirrors power by 2-10 times in a smaller area depending on the size. This also opens the door to using larger mirrors vs many tiny ones.
The goal behind a weapon is deterrence theory. This pointed at a person would make fighting impossible. You start to burn in 3 seconds. You CANNOT STAND IN THIS BEAM....AT ALL!!!!.
Much has been made about how great todays mirrors are vs polished metal mirrors. Metal mirrors offer the advantage of being a true "FIRST SURFACE MIRROR". All glass mirrors are second surface so you lose about 10% reflective power as the light is absorbed by the glass. This would flatten the curve of mirror quality.