He bent his bow is the same as in 2.4. See there for comments. In both passages the sufferer pictures himself as God’s victim in the same terms as are used by Job in Job 6.4; 16.12, 13. Set me as a mark or “made me his target” pictures God as an archer using the poet for his target practice. In areas in which the bow and arrow are not known, a substitute weapon may have to be used. A throwing weapon will retain something of the imagery.

Quoted with permission from Reyburn, William D. A Handbook on Lamentations. (UBS Helps for Translators). New York: UBS, 1992. For this and other handbooks for translators see here .