I think those would have to be case-hardened or something; rebar isn't usually hardenable in itself. AIUI mediaeval arrowheads were sometimes hardened and sometimes not; I guess if you're using them for e.g. hunting unarmoured rabbits there's not the need.
One of the most underestimated arrowheads is the flathead arrowhead , i have a friend who tested a barbed arrowhead and a flathead that he forged himself , it was tested that the flathead produced a massive shock and destroyed meat when hit, think of it as a mini hammer head flying at you at high speeds
