The lifetimes of the 3.39 MeV 6⁺ state in ⁵⁶Fe( tau =4.2+or-0.3 ps) and of the 4.81 MeV ¹⁷/₂^- state in ⁵⁷Co( tau =14.3+or-0.3 ps) have been measured with the heavy-ion plunger technique. The retardations of the 6⁺ to 4⁺ and ¹⁷/₂^- to ¹³/₂^- E2 yrast transitions have been traced to different shell-model signatures of the initial and final states.